Physics Grade -10 (Science )
Physics Grade - 10
(Science )
Unit Topics
2 Pressure
3 Energy
4 Heat
5 Light
6 Current Electricity and Magnetism
Specification Grid
-2074
|
Areas |
S.N. |
Units |
Total
no. of questions & their marks |
Remarks |
||||
|
K-20% |
Un-35% |
Ap-24% |
HA-21% |
Total |
||||
|
Physics |
1 2 3 4 5 6 |
Force Pressure Energy Heat Light Current Electricity & Magnetism |
5x1= 5 |
4x2= 8 |
2x3= 6 |
1x4= 4 |
23
marks |
Physics-56+ Chemistry-56+ Biolog-56+Geology &Astronomy-12 Periods=180 periods |
|
6 |
|
5 |
8 |
6 |
4 |
23
marks |
||
Scholastic Areas :-Grading on 9 points Scale
|
S.N. |
Marks range |
Grade |
Attributes |
Grade
Points |
Remarks |
|
1 2 3 4 5 6 7 8 9 |
90 to 100 80 to below 90 70 to below 80 60 to below 70 50 to below 60 40 to below 50 40 to below 50 30 to below 40 0 to below 20 |
A+ A B+ B C+ C D+ D E |
Outstanding Excellent Very good Good Satisfactory Acceptable Partially Acceptable Insufficient Very insufficient |
4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 0.8 |
The minimum qualifying grade in all subjects under scholastic Domain Is C |
Unit -
1 Force
Force :-A physical quantity which change the state of an
object is called force. Its S.I. unit (N). It is a vector
quantity. Eg. Pulling force, Gravitational force
etc.
Force(F)=Mass(m)×acceleration(a)
or mass(m)×acceleration
due to gravity (g)
Gravitation
or Gravitational force:-The force of
attraction between any two heavenly bodies is called gravitational
force. Its S. I. unit is Newton(N).
Gravitational force(F)=Gm1m2/d2
Where m1=mass of 1st body ,m2=mass of 2nd body ,d=distance between two heavenly bodies
Factors affecting gravitational force:-
1)Mass of 2 heavenly bodies
2)Distance between two object from their
center
Newton’s law of gravitation:-The force of attraction between two heavenly is directly proportional to the product of masses ,and inversely proportional to the square of distance from their center is known as Newton’s law of gravitation.
F∞m1m2 ― i
F∞1/d2 ― ii
This law is applicable for all objects and every where in this universe ie terrestrial or celestial so, it is called Newton’s universal Law of gravitation.
Consequences
or effects of gravitational force :-
i) Existence of solar system and galaxies.
ii)Revolution of planets around the sun.
iv)Formation of tides in the ocean and sea Ievel i.e.gravitational force of moon.
Application of gravitational force or Newton’s
law of gravitation:-
i) It help to determine the
mass of earth and other
heavenly bodies.
ii) It help to calculate the distance between any two heavenly bodies.ie earth and moon.
iii). It help to discovering new planets stars and other heavenly bodies.
Prove that F=Gm1m2/d2
Suppose, Mass of 1st body=m1
Mass of 2nd body =m2
Distance between two heavenly bodies from their
center=d
If force of attraction between them=F
Now, according
to Newton’s law of gravitation.
F∞m1m2
F∞1/d2
Combining eqn
( i) and eqn (ii)
F∞Gm1m2/d2
Or, F=Gm1m2/d2 (where G is
universal gravitational constant)
؞F=Gm1m2/d2 Proved
Combining eqn
( i) and eqn (ii)
F∞Gm1m2/d2
Or, F=Gm1m2/d2 (where G is
universal gravitational constant)
؞F=Gm1m2/d2 Proved
Gravity:-The force by which a
heavenly body ie. Earth attract another body
towards the center of its is called gravity. Its S.I. unit is Newton’s (N) ie. The force of attraction of earth on
us.
Gravity(F) = GMm/R2
Where ,M=Mass of heavenly
body ,m=Mass of object lying on the surface of heavenly body, R=Radius of
heavenly body.
Consequences or effects of gravity:-
i)Presence of weight in
every body.
can stand and walk on the surface of earth.
iv)The earth is surrounded
by the atmosphere .
v)Acceleration is produced
in freely falling object.
Prove that g∞1/R2
Suppose ,Mass of an object lying on the surface of earth=m
Mass of earth =M
Radius of earth=R
According to Newton’s law gravitation
F=GMm/R2 ㅡ i
According to Newton’s second law motion ,the force of gravity acting on the body.
F=mg ㅡ ii
Equating the relation of
eqn(i) and eqn (ii)
mg=GMm/R2
or, g=GM/R2
or, g∞1/R2 (where G and
M are constant)
؞g∞1/R2
Proved.
(Thus, acceleration due to
gravity is inversely proportional to square of distance from the center of
heavenly bodies)
Acceleration due gravity:-
The acceleration produced in freely falling object towards the surface of earth due to influence of gravity is called acceleration due to gravity. Its symbol is g and S.I. unit is m/s2.The value of g at poles of earth is 9.83m/s,2 equatorial region is 9.78m/s2 and centre of earth is 0m/s2.It acts towards the centre of earth or the direction of acceleration due gravity is always downwards I.e. towards the centre of heavenly bodies.
Acceleration
due to gravity(g)=GM/R2
Where,
M=mass of heavenly bodies ie. Earth, m=mass of object lying on the surface of
heavenly bodies ie. Earth.
Note:- The value of acceleration due to gravity of earth=9.8m/s2,Moon =1.6m/s2,Jupitor =25m/s2
Variation
of g with height from the surface of earth :-
Consider the mass of the earth be M,
and radius R respectively. The acceleration
due to gravity on the surface of earth is given by
Now ,g’ be the acceleration due gravity
g’/g=GM/(R+h)2 =R2/GM
or g’/g=(R/R+h)2
Q.1)What do you mean
by the statement the acceleration due to gravity of earth is 9.8m/s2?
Ans : It means that earth produce an acceleration of
9.8m/s2on freely falling object towards the
surface of earth under the influence
of gravity.
Q.2)If an iron ball and
feather are dropped simultaneously in vacuum which one will strike the ground
first and why ?
Ans: Both iron ball and feather will reach the ground
simultaneously because if there is no
external resistance .
Universal gravitational constant(G):-
The gravitational force between two unit of masses kept at 1metre distance is called universal gravitational constant(G).Its SI unit is Nm2/kg2and value is 6.67x10-11 Nm2/kg2.It is constant all over universe .It is a scalar quantity.
 |
The experiment was first performed by Robert
Boyl in 1590 to verify idea of Galileo when all object
is dropped from same height at same
time strike ground together.
In
the experiment coin and feather are kept in a long
glass tube and tube is quickly inverted then ,the air inside the tube is
removed with vacuum pump and same experiment is
repeated. when air inside the tube coin reach other end
faster than feather but when there is no air or vacuum both coin and father reach the other end at the same time.
Conclusion
of coin and feather experiment:
Coin and feather experiment conform that if there is
no external resistance all bodies falls towards the
surface of earth with same acceleration.
Q 1)A feather and coin falls
together on the surface of moon why?
Ans. There is no air on the surface of moon
therefore a feather and coin falls together on the surface of moon due to same
acceleration due gravity in all object.
2.)Why is the value of g differ
from place to place on the surface of earth?
Ans. The value g depend on radius of the earth, and radius of earth is differ
from place to place on the surface of earth. Therefore the value of g is differ
from place to place on surface earth ,because we know
that g∞1/R2
3.)Why is the value of g is
more at polar region than that of equatorial region on the surface of earth ?
Ans.)The value of g depend on the radius of earth and
radius of earth is more at equatorial region than that polar region, therefore
the value of g is more at polar region than that of equatorial on the surface
earth, because we know that g∞1/R2.
4.)Why is the value of g is
more at terai region than that of mountains or Himalaya region?
5.)Why is the weight of
object is differ from place to place on surface of earth?
Ans.)The weight of an object depend on the value of g
and value g depend on the radius of earth, and the radius of earth is differ
from place to place on the surface of earth, therefore the weight of an object
is differ from place to place on the surface of earth.
6.)Why is weight of object
more at Terai region that of mountains region ?
Ans. The weight of object depend on value g and value g depend on radius earth and of earth is more at mountains
region than that of Terai .Therefore the weight object is more at Terai region
than that of mountains region, because we know that
w∞g∞1/R2.
7.)Why is weight of object
more at polar region than that equatorial region on the surface of the earth?
Ans. The weight
of the object depend on the value of g and more at equatorial region than that
of polar region of earth of earth. Therefore ,the weight of object is more at
polar region than that of equatorial region of earth ,because we know that w∞g∞1/R2.
Gravitational field intensity:-The
total force gravity experiences by unit of masses kept on the surface of
heavenly bodies is called gravitational field intensity .Its S.I. unit N/Kg and its value is 9.8
N/kg on surface of earth.
Gravitational field intensity (I) =GM/R2
Where
M=mass of heavenly body, R=radius of
heavenly body.
1.)What do you mean by the statement that the
gravitational field intensity of earth is 9.8N/Kg?
Ans.It
means that 1kg of mass experiences 9.8N force
gravity kept on surface of the earth.
2.)Differences between mass and weight.
|
Mass |
Weight |
|
1.The total amount of matter contained in abody is called mass. 2.It is a fundamental quantity. 3.Its SI unit is Kg. 4.It is measured by beam balance. 5.It is a scalar quantity. 6.It is constant all over the universe. Mass(m)=W/g |
1.The of amount of force gravity acting on a body is
called weight. 2.It is a derived quantity. 3.Its SI unit is N. 4.It is measurement by spring balance. 5.It is a vector quantity. 6.It is variable place to place. Weight(W)=mg |
Free fall:-If an object is falling without external resistance
is called free fall.
Or
If an object is falling with acceleration due to gravity in the absence of air is called free fall .Eg .body falling in vacuum ,body falling on the surface of moon ,body falling in the acceleration due to gravity .In every free fall there is weightlessness.
Weightlessness:-The condition in which the weight of an object is zero is called
weightlessness .All free fall is weightlessness but all
weightlessness are not free fall.
Or
The condition in
which the an object is not attracted by any force is called
weightlessness.eg At the center of earth, in an
artificial satellite, during free fall at null point.
Condition of weightlessness:-
1.)A body is weightlessness, When body is falling freely because reaction
force is zero. It is apparent weightlessness.
2 .)A body is weightlessness, when body is in the
space or null point ,because the value of g
=0m/s2 or gravitational pull of earth is equal to the
gravitational of moon. It is perfect weightlessness.
3. A body is weightlessness, when a body is in
the rocket which is orbiting around heavenly body, because body is in
rocket in state of free fall.
4.) A body is weightlessness, when a body is in
the centre of earth.
1.)The
fall of a parachute toward the earth surface is not a free fall” ,justify this
statement .
Ans. A body is said to have free fall, if it does not
experience any kind of resistance during falling .but when parachute falls towards
the surface of earth, it experience up thrust of air from opposite
direction ,therefore falls of parachute is not free fall.
2.) How does parachute
fall ?explain.
Ans. When parachutist jump at first speed of parachute goes
on increasing due to effect of gravity same time parachute open due to up
thrust of air then after certain time magnitude of
gravity and up thrust of air from opposite direction become equal and velocity remains constant ,acceleration
will be zero so parachute falls towards earth slowly with low velocity.
3.)A
parachutist is not hurt jumps from at great height ,why?
Ans. When parachutist jumps from at great height due its large
volume experience equal magnitude of up thrust of air
from opposite direction to the acting on the parachute. Therefore
falling slowly with low velocity towards the surface of earth and does not get
any hurt.
4.)What
is difference in the falls of parachute on the surface of earth and moon.
Ans. On the surface of earth parachute does not freely
falls due to presence of air ,but on the surface of moon object falls freely
due to absence of atmosphere.
5.)Weight
of object is less in mine of coal ,why ?
Ans. The weight object depends on the value of g and
value of g depends on the depth from the surface of earth ,while going downward
in mine depth of earth increases ,value of g decrease so the weight of an
object decreases because we know that weight∞g∞1/depth
6.)What
change is seen on acceleration due gravity as we move towards the centre of earth.
Ans. When we move towards the centre of the vale of g
goes on decreasing and centre of earth value g is zero. because we know that g∞1/depth of the surface of earth
7.)The
probability of hurt is more when a person jumps from a significant height ,why?
Ans. If person jumps from a certain height ,his acceleration goes on
increasing towards the earth surface and force is
directly proportional to acceleration due to gravity so the more
acceleration more will strike force .Therefore the of getting hurt is more when a person jumps from a
significant height .
Numerimcal problems
F=Gm1m2/d2 ― i)
F=GMm/R2 ㄧ ii)
g=GM/R2 ㅡ IIi)
g=GM/(R+h)2 ㄧ iv)
W=mg ㅡ v)
g’=(R/R+h)2×g ㄧ vi)
h=ut+1/2gt2 ㅡ Vii)
v2=u2+2gs ㅡ viii)
Wt. lift on the surface of earth=wt lift on the surface of moon
WE=WM or mgE=mgm ㄧ ix)
Jump on the earth surface(h)×gE= Weight lift on the moon surface(h)×gM ㅡx
1.)What is gravitational
force when the distance the object is made double ?
From Newton’s law
of gravitation
F=Gm1m2/d2 ㅡ i)
According to question.
M1=m1, m2=m2 ,d=2d
According to Newton’s
law of gravitation
F’
=Gm1m2/d2
0r
F’ =Gm1m2/(2d)2
0r
F’= Gm1m2/4d2
Or
F’= 1(Gm1m2)/4d2
From
equn(i)
F’=1F/4
؞The force will be 1F/4 the initial force.
2.)What change in
gravitational force is seen when masses and made double and distance is halved
.
From
Newton’s law of gravitation
F=Gm1m2/d2 ㅡ i)
According to question
M1=2m1 ,m2=2m2 ,d=d/2
According
to Newton’s law of gravitation
F’=Gm1m2/d2
Or
F’=G2m12m2/(d/2)2
Or
F’=4(Gm1m2)/d2/4
Or
F’=4×4(Gm1m2)/d2
From
eqn (i)
F’=16F
؞The force will be 16F the initial force.
3.)Gravitational force or
weight produced between two bodies is 5N when they are at the distance of
5m.How much gravitational force or weight is produced when they are at distance
of 10m.
Given,
1st condition
Gravitational force (F1)=5N
Distance (d)=5m
From Newton’s law of gravitation
F1=Gm1m2/d2
Or 5=Gm1m2/52
؞Gm1m2=5×25 ㅡ i)
2nd condition
distance (d)=10m
gravitational force (F2)=?
From Newton’s law of
gravitation
F2=Gm1m2/d2
0r F2=5×25/102
Or F2=125/100
؞F2=1.25N
Gravitational force of 1.25N is produced when given object is kept at 10m distance.
4.)Gravitational force
produced between two bodies is 5N what will be the new gravitational force if
the distance between them is (i)Halved
(ii) doubled.
Given ,
1st condition
Gravitational force(F1)=5N
From Newton’s law of gravitation
F1=Gm1m2/d2
5=Gm1m2/d2 ― i)
i)2nd condition
Distance(d)=d/2
Gravitational force (F2) =?
From
Newton’s law of gravitation
F2=Gm1m2/d2
0r F2=Gm1m2/(d/2)2
Or F2=Gm1m2/d2/4
Or F2=4(Gm1m2/d2)
From eqn (i)
F2 =4×5
؞F2=20N
Gravitational force of 20Nis
produced when given object is kept at halved distance with initial distance.
(ii)2nd
condition
Distance(d)=2d
Gravitational force (F2) =?
From Newton’s
law of gravitation
F2=Gm1m2/d2
Or F2=Gm1m2/(2d)2
Or F2=Gm1m2/4d2
Or F2=1/4(Gm1m2/d2)
From eqn (i)
Or F2=1×5/4
؞ F2=5/4N
Gravitational force of 5/4N is produced when object is kept at doubled distance with initial distance.
5.)If a person can lift a
load of 60kg on the surface of earth .How much load can lift on the surface of
moon .(gE=9.8m/s2 and gM=1.66m/s2)
Given,
Mass lift on earth(m)=60kg
Acceleration due to gravity of earth(gE)=9.8m/s2
Acceleration due to gravity of moon(gM)=1.66m/s2
Mass lift on moon (m)=?
By formula
Weight lift on earth (WE)=Weight
lift on moon(WM)
MgE=MgM
Or 60×9.8=M×1.66
M=60×9.8/1.66
؞Mass lift on the surface of moon (m)=354.21N
6.)A man is capable of
jumping 1m on the surface of earth .How height does he jumps on the surface of
moon.?(gE=9.8m/s2 and gM=1.66m/s2)
Given,
Jump on the earth (h)=1m
Jump on the moon (h) =?
By formula
Height jump on earth(h)×gE
= height jump on moon(h)×gM
Or 1×9.8 =height jump on
moon(h) ×1.66
Or height jump on moon(h)=1×9.8/1.66
؞Height
jump on the surface of moon(h)=5.90 or 6m
7.)What is force of
attraction between two object each of mass 1kg separated by 1m distance ?
Given,
Mass of 1st object (m1)=1kg
Mass of 2nd object(m2)=1kg
Distance(d)=1m
Gravitational force (F)=?
By formula
F=Gm1m2/d2
Or F =6.67 ×10-11×1×1 /12
Or, F=6.67×10-11 N
؞Gravitational force(F)=6.67×10-11N
8.)The mass of venus and sun are 4.89×1024kg and 2×1030kg
respectively and distance between them is 1.072×108km.Find out the
gravitational force between them.
Given
Mass of venus(m1)=4.89×1020kg
Mass of sun (m2)=2×1030kg
Distance(d)=1.072×108km
=1.072×1011m
Gravitational force (F)=?
by formula,
F=Gm1m2/d2
Or ,F=6.67×10-11×4.89×1024×1030 /(1.072×1011)2
Or,F=65.23×1043 /
1.14×1022
Gravitational force(F)=5.72×1022N
9.) If the mass of mars is 6×1023kg
and that of earth is 6×1024kg and the gravitational force between
them is 6.67×1016N,calculate the distance between their centers ?
Given,
Mass of mars (m1)=6×1023kg
Mass of earth(m2)=6×1024kg
Gravitational force (F)=6.67×1016N
Distance (d)=?
By formula
F=Gm1m2 / d2
or 6.67 ×1016= 6.67×10-11×6×1023×6×1024
/ d2
d2
= 6.67×10-11×6×1023×6×1024 / (6.67×1016)2
d2 =36×1020
d= 6×1010m
Distance (d)=6×1010m
10.) The Mount Everest is
8848 m above the sea level. What is acceleration due gravity at this height? If
the value of acceleration due to gravity at the gravity at the earth
surface is 9.8m/s2 and radius
of earth is 6.4×106.
Given,
Height of Mount Everest (h)=8848m
Acceleration due to gravity
surface(g)=9.8m/s2
Acceleration due to gravity at
height(g’)=?
Radius of earth (R)=6.4×106m
By formula
g’ =(R/R+h)2×g
g’ =(6.4×106/6.4×106+8848)2×9.8
or g’ =40.96 ×1012 ×9.8 / 41.07×1012
Or Acceleration due to gravity( g’ )=9.78 m/s2
11.)The mass and radius of
earth are 6×1024 and6.4×106m respectively. Calculate the
acceleration due to gravity at the top of Mt. Everest of height 8848m from the
sea level .Also find out the weight of a person whose mass is 80kg on the
height.
Given,
Mass of earth(M)=6×1024kg
Radius of earth(R)=6.4×106m
Height (h)=8848m
Mass of man(m)=80kg
Acceleration due gravity(g)=?
By formula
g =GM/(R+h)2
or g = 6.67×10-11×6×1024 /(6.4×106+8848)
Or g=
40.02×1013 / (6408848)2
Or g=
40.02×1013 / 4.10×1013
g=9.76m/s2
Acceleration due to gravity
at the top of Mt. Everest =9.76m/s2
Also,
Weight of man(w)=m×g
=80×9.76
=780.8N
12.)What should be height
from the surface of earth so that we can get the acceleration due to gravity
6m/s2.The mass of the earth and radius are 6×1024kg and
6400km respectively.
Given,
Acceleration due to gravity at
height(h)=6m/s2
Mass of earth(M)=6×1024kg
Radius of
earth(R)=6400km=6400×1000m=6.4×106m
Height from the earth surface(h)=?
By formula
g = GM/(R+h)2
or 6 =6.67×-11×6×102 / (R+h)2
or (R+h)2 =40.02×1013 / 6
Or (R+h)2 =66.7×1012
Or R+h =
Or R+h =8.16×106
Or h =8.16×106-R
Or h =8.16×106-6.4×106
؞ Height (h)=1.76×106m
Therefore at the height of 1.76×106m from the earth surface we get acceleration due to gravity of 6m/s2.
13.) The mass of Jupiter is
319 times greater than the mass of earth and the radius is 11times greater than
the radius of earth .If the acceleration due to gravity on the earth surface is
9.8m/s2.Calculate acceleration due to gravity on the surface of
Jupiter .
Given,
Mass of Jupiter (Mj)=319ME
Radius of Jupiter(Rj)=11RE
Acceleration due to gravity of earth(gE)=9.8m/s2
Acceleration due to gravity of Jupiter
(gj)=?
According to Newton’s law of
gravitation
gE =GME/RE2 for earth (i)
gJ =GMJ/RJ2
For jupiter (ii)
Dividing eqn
(i) by eqn (ii)
gE / gJ
=GME ×RJ2 /
GMJ×RE2
gE / gJ =GME× (11 RE)2 /
G319ME×RE2
or gE/gJ
=121/319
gJ = 319×9.8 /121
؞ Acceleration due to gravity on the surface of Jupiter (gJ) =25.83 m/s2
14.)A stone is dropped
freely from 20m height of tower .If reach ground in 2 sec. .Calculate the
acceleration due gravity of that stone .
Given,
Initial velocity (u)= 0m/s
Height (h) = 20m
Time taken (t) =2 sec
Acceleration due to gravity(g) =?
By formula
Height(h) =ut +1/2 gt2
Or 20 =0×2+1/2×g×22
Or 20 =0+2g
Or g =20/2
؞Acceleration
due to gravity (g)=10 m/s2
15.)A body thrown vertically
from earth surface and took 16 sec. to
return to its original position .find out the initial velocity (The resistance
is considered as zero)
Given,
Final velocity (V)=0m/s
Acceleration due gravity (g) = -9.8
m/s2
Time taken to reach its height (t)=16/2 =8 sec.
Initial velocity(u) = ?
By formula
V =u+gt
Or 0 =u+(-9.8)×8
؞u
=78.4 m/s
Therefore initial velocity
(u)=78.4m/s
Unit - 1
Group –A (1 mark each )
1.State the Newton's universal law of gravitation.-(SEE 2074)
2.Write one effect seen on ocean or sea due to gravitation of
the moon and the sun. [SLC 2069 C, 2068 A]
3.What is the value of universal gravitational constant (G) ? [SEE 2074 (CC)]
4.What is the gravitational constant ? Write its value. [SLC 2065 A, 2067 E, S, 2068 E, 2070E, 2072 FW, SEE Model
Question 2074]
5.Write down unit of gravitational constant..[SLC 2072 FW, 2071 B]
6.In which direction does the force of gravity act ?[SLC
2069 A]
7.Why do the satellites not fall while revolving around the
earth ?[SLC 2069 A]
8.What is the value of acceleration due to gravity 'g' at polar
region ?(Ans: 9.83 m/s2) [SLC 2071 D]
9.What is the value of 'g' on equatorial region and polar region
of the earth?[SEE 2074 (BC)]
10.What is acceleration due to gravity? [SEE 2073 MA]
11.Where does the weight of a body become maximum on the surface
of the earth ?
[SLC 2069 E]
12.At what condition does a coin and a feather fall together? [SLC 2069 B, 2065 B]
13. When a feather and a coin is dropped towards the surface of
earth, do they reach the ground together? [SLC 2070
B]
14.What is weightlessness ? [SLC
2070 A, 2065 A, 2063 C]
16.Give a condition in which an object becomes weightless.[SLC
2070 A, 2065 A, 2063 C]
17.Write down definition and the unit of acceleration due to
gravity 'g'.
[SLC 2072C, 2071 S, 2063 A]
18.What is gravity? [SLC 2068 B,
2066 E]
19.What is the value of acceleration due to gravity at the
equatorial region of the earth? (SLC 2068 B, 2066 E]
20.What is free fall ? [SLC 2072 E, 2071 A, 2068 D]
Goup- B (2 Marks Each )
1.Tides rise on the sea, why? [SLC 2070 C]
2.The effect of gravitation is more in liquid than in solid, why [SLC
2069 E]
3.A satellite does not need any energy to revolve around the
earth, why ? [SLC 2071 C]
4.The value of gravitational constant is 6.67x 10-11 Nm2/kg2.
What does it mean?
5.Under which condition the value of gravitational force and
gravitational constant becomes equal? [SLC 2071 S] [SLC
2063 A]
6.What is the relation of force of gravitation with masses of
the objects and distance.
7.Write any two differences between gravity and gravitation. [SLC 2071 B, 2068 C]
8.List two differences between universal gravitational constant
(G) and acceleration due to gravity . [SLC 2072 W,
2070 S, 2063 D, 2058 A]
9.It is difficult to lift a large stone on the surface of the
earth but easy to lift small one, why? (SLC 2065 A]
10.Explain on the basis of Newton's law of gravitation that the
weight of an object farther from center of the earth is lesser. [SLC 2067 S]
11.The acceleration due to gravity on the surface of the Jupiter
is 25m/s2. What does it meant ? । [SEE
2073 SP]
12.Where does the weight of a body become maximum in Nepal? Why? [SLC 2069 C]
13.Why is the value of 'g' more in terai than in the mountain? [SEE 2074 (CC)]
15.The weight of a body is less on the moon surface than on the
earth surface, why? [SLC 2071 C]
16.How much is the weight of a body less on the moon surface
than on the earth surface? Why? (SEE 2074 (BC)]
17.A stone and piece of paper are dropped simultaneously from
the same height on the lunar surface, which one will fall faster ? Why? । (SLC
2071 A]
18.A piece of stone and a feather are dropped from the same height
at Lunar surface, which one will reach on the surface fast and why? [SLC
2067 C]
19.State the relation between radius of the earth and its
acceleration due to gravity. [SLC 2062 C]
20.Write the reason behind that atmosphere does not escape away from the earth.[SEE2073 SP]
21.Acceleration due to gravity varies according to places of the
earth, why? [SLC 2070 B]
22.Why does the value of g is more in polar region than in equator
[SLC 2072 C]
23.What effect will be on
acceleration due to gravity if radius of the earth is decreased ? [SLC
2068 D] [SLC 2062 E]
24.Givereason why an object weighs more in Terai region than in Himalayan region.
25.Weight of a body is found less at the top of mountain than at the
bottom of it, why?[SLC 2063 E]
26.Write any two differences between gravity and acceleration
due to gravity.
[SEE 2073 SP]
27.We do not get hurt, when we jump with parachute, why? [SLC 2068 B, 2059 S]
28.Why does a sheet of paper fall later on the earth surface
than that the paper ball of equal weight if thrown from a certain height? [SLC 2069 D
29.At what condition does a coin and a feather fall together?
What is the acceleration of the feather and the coin at that instant ? Justify
your answer.- [SLC 2069 B, 2065 B]
30.When a feather and a coin is dropped towards the surface of
earth, do they reach the ground together? If this experiment is done in moon,
what difference can be occurred ? Write with reason. [SLC 2070 B]
31.A feather and a coin when dropped from a height on the
surface of the moon, they fall simultaneously, why? [SLC 2065 C & D]
32.What is the difference between fall of a parachute on the earth
and that on the moon ? What is the effect of gravity on the falling object ? [SLC 2066 B, 2062 B]
33.Weight of an object is greater at the polar region than the
equatorial region of earth, why? [SLC 2072 W,
2068 5, 2063 B, 2060 D, 2059 S]
34."The acceleration due to gravity on the surface of earth
is 9.8 m/s2." What is its meaning? [SLC 2070 D]
35.The value of acceleration due gravity in moon is 1.67 m/s2.
What does it mean?
[SLC 2072 E]
36.A large stone of 20 kg and small stone of 5 kg are dropped
simultaneously from certain height. Which one will reach on the ground first?
Why?
(SLC 2071 E]
37.Stone of 1kg and 5kg masses are dropped from the same height
at lunar surface, which one will reach on the surface fast and why? [SLC 2066 A]
38.A paratrooper lands safely when jumped from a great height,
why?
[SLC2061 A] 101
39.Why can't we fall safely with the help of parachute towards
the Moon?
(SLC2072 FW]
40.Theprobability of getting hurt is more when a man jumps from a significant height,why? [SLC 2067 B]
41.Write two difference between free fall and weightlessness.[SLC
2071 D]
[SLC 2058 D]
42. Will the value of acceleration due to gravity be greater at
Terai or at the Mountain ? Why
43.Why does the weight of an object decrease with increase in
distance from the centre of the earth? (SLC 2058 C)
44.What is the direction of acceleration due to gravity ? State
with reason.
[SLC 2058 D]
Group-
C (3 Marks Each )
1.Find out the change in gravitational force between two
bodies of fixed mass, when place at double distance. [SLC
2068 B]
2.What change occurs in the gravitational force between two
bodies when mass of each is made double and distance between their centres is
halved? Calculate.
(Ans: 16
times) [SLC 2072 FW, 2069 B]
3.The mass of the moon is 7.2x1022 kg and its radius
1.7x106 m. Calculate the acceleration due to gravity of the moon and
also calculate the weight of an object of mass 80 kg on the lunar surface.
(Ans: 1.66m/s2, 132.8N) [SEE 2074
(BC)]
4.Ameteor is falling towards the earth. If mass and radius of the earth are 6 x 1024kg and 6.4 x 103 km respectively, find the height of meteor from the earth's surface where its acceleration due to gravity becomes 4m/s2.The weight of a body decreases in a coal mine, why?(Ans:3600
km) [SEE 2074 (DC))
Group –D (4 Marks Each)
1.What happens to the weight of an object when it is taken from
earth to the moon? Why?
2.If a body is dropped from the same height once in the equator
and then in the polar region, in which place will it fall faster? Explain with
reason.
[SLC 2063 C]
Unit -
Test
Unit
1: Force (बल)
Time: 40 min. F.M.: 22
सबै प्रश्नहरूको
उत्तर
दिनुहोस्
।
(Answer all the questions.)
समूह 'क' (Group
'A') 1x6 =6
1.State Newton's universal law of gravitation.
2.What is the relation between the gravitational force acting
between any two objects with their mass and the
distance between their centres ? Write. .
3What is acceleration due to gravity ? In which unit is it
measured ?
4.Onwhich factors does the mass of an object depend?
5.What is a free fall ?
6.In which condition does a body of certain mass become weightless
?
समूह 'ख' (Group
'B') 3x2=6
7.Write any two differences between acceleration due to gravity and
gravity.
8.Theweight of a body is more at the polar region of the earth than that at the equatorial region. Why?
9.Write any two differences between mass and weight.
समूह 'ग' (Group
'C') 2x 3 =6
10.What change occurs in the gravitational force between two
bodies when mass of each is made double and distance between their centres is halved? Calculate.
11.The mass of the jupiter is 1.9 x 1027 kg and its
radius is7.1 x 104 km. Calculate the acceleration due to gravity on
the surface of the jupiter. What will be the weight of the person of mass 85 kg
on that planet?
समूह 'घ' (Group
'D') 1x 4 =4
12.Why does the value of g is more in polar region than in equator A person lifts 60kg on the surface of the earth. How much mass can he lift on the surface of the moon if he applies same magnitude of force?(Ans:362.96 kg)
Unit- 2
Pressure
Pressure:-The force acting normally on per unit area is called
pressure .Its S.I. unit Pascal or N/m2.It is a scalar quantity.
Pressure
(P)= Force(F)/Area(A)
P = F/ A
Relation
between pressure ,force and area:-
i)When force
is applied more pressure will be more and when force is applied less pressure
will be less. If area is kept constant.
P∞F (i)
ii)When force
is applied on greater area pressure will be less and when force is applied on
less area pressure will be more. If force is kept constant.
p∞1/A
(ii)
I Pa Pressure: The
pressure produced by applying 1N force on 1m2 area is called 1 pa
pressure.
1
pa = 1N/1m2
Prove that P= F/A
P =Pressure, F = force , A
=Area
According to relation between pressure
,force and area.
P∞F (i)
P∞1/A (ii)
Combing eqn (i) and (ii)
P∞F/A
P = KF/A (where k is constant)
Or P= KF/A (iii)
According to definition 1 Pa ,if F = 1N, A = 1m2 then P
= 1pa
Now, we get
1 =k.1 /1
؞K =1
Again,
Putting the value of k in
eqn (iii)
Or P = 1 F/A
Difference
between force and pressure
|
Force |
Pressure |
|
1.)A physical quantity that change the state
of an object. ii) its S.I. unit N iii) It is a vector quantity. iv) Force(F) =mass ×acceleration(a) or
acceleration due to gravity(g) F =m× a or g |
1.)The force acting normally on per unit area is called
pressure . ii) Its S.I. unit is pascal. iii) It is a scalar quantity. iv) Pressure (P)= Force(F)/Area(A) P = F/A |
1.)A
man exerts more pressure when he stand with one foot than when he stand on two foots, why ?
Ans. The area of one foot is less than that of two foots so a man exert more
pressure he stand with two foots than with one foot ,because we know that
P∞1/A .
2.)Basses and truck have broad and
double wheeled tyeres, why?
Ans. The areas of broad or doubled tyeres is more so
give more less pressure on road and easily can carry heavy load .Therefore
busses and trucks have broad and doubled tieres, because
we know that P∞1/A
3.The studs are made on the sole of football player’s boot ,why?
4.)The backside wheel of tractor are
made larger and flat ,why?
Ans. The larger and flat wheel have more area, so give less
pressure on the road and can easily move during ploughing, threshing etc.
Therefore backside wheel of tractor are made larger and flat, because we know that P∞1/A.
Liquid pressure:- The thrust exerted by a liquid per unit area is
called liquid pressure .Its S.I. unit Pascal or N/m2.
Liquid Pressure (P) = d×g×h
Where d=
density of liquid ,g = acceleration due to gravity , h = depth of liquid
Factor affecting liquid
pressure:-
i)density of liquid(d)
ii)Acceleration due to gravity (g)
iii)depth of liquid (h)
General laws of liquids pressure:-
i)The pressure
of liquid is directly proportional to the depth of liquid. P∞h
ii)At the same
depth the pressure of the liquid is same in all direction .
iii)Pressure
of liquid is directly proportional to density of liquid . P∞d
iv)The
pressure of liquid does depend upon the shape and size of container .
v) The liquid
finds its own level .
Prove that P=d×g×h
According to
definition of pressure
P =F/A
Or P =m×g/ A ( F=mg )
Or P = d×v×g/ A (m=d×v)
Or P = d×g×A×h/ A (V =A xh)
1.)The speed of flow of water out of a tap of up floor is less than that
of the down floor ,why ?
Ans. The depth
of liquid column of down floor is more than that of up floor. Therefore speed
of flow of water is more at tap of down floor than that of tap of up floor, because we know that P∞d .
2.)What change in the pressure at the bottom of a drum filled with
water. If it is brought to Himalaya from terai ?write with reason .
Ans. The
pressure at the bottom of drum decrease, if water filled drum is brought from
terai region to Himalaya region because The value of g is less at Himalaya
region than that Terai region, We know that P∞g .
3.)While the building a dam
for water reservoir the base is made wide, why ?
Ans. The depth
liquid column of base of dam of water reservoir is more than that of upper
portion,so base liquid column give more
upthrust than that of upper portion. Therefore base of dam of water reservoir
is made wide .because we know that p∞h
4.)As the given fig the
tank with capacity 1000 liter has greater cross sectional area than that with
capacity 500 liter. Answer the following questions.
i)Whose bottom experience more pressure, if both contain equal
volume of water ?
Ans. The 1000L tank of bottom experience less pressure than that of 500 L tank
of bottom because due to more cross sectional area of 1000L tank the depth of
liquid column less than that of 500L tank because we
know that P∞h
ii) If depth of water are
equal in both which one experience more pressure at the bottom?
Ans. If both contain same depth
of water the pressure exerted on the bottom of tank will be same.
iii) On which factors does the pressure of liquid depend ?
Ans. The liquid pressure depend on following factors ie
i) density of liquid(d) ii)Acceleration due to gravity(g) iii) depth of
liquid(h)
Upthrust :- When a body is immersed in a liquid exert an upward force on the body is called upthrust. Or
An upward force is experienced by an object ,when it is partially or wholly immersed in a liquid is called upthrust or buoyant force . its S.I. unit is N.
Upthrust (U)=d×g×h×A
Where, d=
density of liquid ,g= acceleration due to gravity, h= depth of liquid ,A = area of the object
Upthrust of liquid = Wt. of body in air –wt of the body in the liquid
Or Upthrust of liquid = loss of wt of object in the liquid
Cause of upthrust:
When a body is immersed in liquid in a liquid the lateral pressure experience by the body mutually cancel each other ,but downward pressure and downward force acting on the body is always than that of upward pressure and force acting on body .Therefore resultant force acting between upward and downward force i.e. cause of upthrust force or resultant force is known as upthrust.
Prove that U= d×g×A×(h2-h1), ( using Archemedes’ principle)
Or U = d×g×h×A
Or U=d×g×v
Or U=mg or w
Or Upthrust =displace of wt. of liquid (w)
Suppose
A
body PQRS of height =h
Cross sectional area =A
Densety of liquid =
Height of liquid column above surface PQ
=h1
Height of liquid column above surface
RS=h2
Pressure exerted on upper surface PQ(P1)=d×g×h1
Or Downward upthrust exerted on upward
surface(F1)=P1×A
Or F1 =d×g×h1×A
Again,Pressure exerted on lower surface
RS(P2)=d×g×h2
Or Upward upthrust exerted on lower
surface(F2)=P2×A
Or F2=d×g×h2×A
؞Resultant force or Upthrust (U)=F2-F1
Or U=d×g×h2×A - d×g×h1×A
Or U=d×g×A(h2-h1)
Or U=d×g×h×A (because h2-h1 =h)
Or U=d×g×v (
because V=A×h)
Or U=m×g (because m=d×V)
Or U = w (because
w=m×g)
1.)An egg float in salt water but sink in fresh water, why?
2.)It more easy to swim in
sea water than that of river water why ?
Ans. The density of salty sea water is than of river water
so sea water gives more upthrust than
that of river water. Therefore it is more easy to swim in sea water than that
of river water ,because we know that U∞d.
3.)It is more easy to pull bucket inside water than air, why ?
Ans. The density of water is more than that of air so water give more
upthrust than that of air. Therefore it is more easy to pull bucket inside
water than that of air because we know that U∞d.
4.)It is difficult to sink an empty plastic bottle in water ,why?
Ans.The density of air filled empty bottle is very less than that of water
so, water give more upthrust than that of empty plastic bottle .Therefore it is
difficult to sink empty bottle in water because we know
that U∞d.
5.) What is the weight of
an object floating on the surface of water? Explain.
Law of floatation:- An object that floats on liquid medium displace the
liquid equal to its weight is known as law of floatation.
Or An floating object displace liquid equal to its weight is known as floatation .
Wt. of displace of liquid = Wt. of the floating an object
Verification of law of floatatio
Now, It is found that
Wt of wooden block = wt of
displace of liquid
W1 = W2
It show that or verify floating object displace liquid equal to its weight
Instruments based on law
of floatation:-
i)Hydrometer ii) Lactometer
1.)An iron nail sink in water but a ship made up iron float in water, why ?
2.) How
much water a girl weighting 450 N should displace in order to float in water .
Ans.A girl weighting 450 N should displace 450N water in order to float in water because according to law of floatation the wt. of floating body = wt. of displace of water.
Pascal’s Law:- When pressure is applied on
the liquid contained in a closed container .It transmitted equally in all
direction is known as pascal’s law .
i)Hydraulic press ii) Hydraulic jack iii) Hydraulic lift iv) Hydraulic break
Hydraulic press:- An U shaped simple machine based on pascal’s law, which convert small force into large force is called Hydraulic Press .It consist of two piston, area of one piston small and other piston is large .
Principle of hydraulic
press:- It
states that ,when small force is applied on small piston it change into large
force on bigger piston .
Characteristics of
liquid on the basis of which hydraulic press is constructed
:-
i)Liquid
transmits pressure equally in all direction.
ii)Liquid is
incompressible .
Uses of hydraulic Press:-
i)It used for
pressing books ,cotton goods.
ii)It is used
for extracting juice of fruits ,seeds etc.
iii)It is used
to gives specific shape to metal and punching hole in metal
iv)It is used
for pressing plywood ,cardboard etc.
Prove that Hydraulic Press
is an effort multiplier, or
F2/F1 =A2/A1
Suppose ,A U shaped vessel contain a liquid is provided with 2
piston, cross sectional area of small piston =A1
Cross sectional area of large piston=A2
Then, force F1 is applied on
small piston and pressure exerted on small piston P=F1/A1
According to pascal’s law pressure
exerted on small piston is transmitted on large piston.
Therefore , Pressure
exerted on large piston =F1/A1
Again,
Upward force exerted on large
piston= F2=P2×A2
Or F2 =F1 ×A2 / A1
Proved
Or A2>A1 gives F2>F1
Therefore, small force F1 can change large force F2 on Large piston o act as force multiplier.
Uses of hydraulic jack:-
Uses of hydraulic break :-
Uses of hydraulic lift :-It
used in hospital ,hotels etc to provide easy service.
Archimedes’ principle:-
It states that
“When a body is body is partially or wholly immersed in a liquid .It experience an upthrust (loss of weight ) is equal to displace of liquid by it”
.
According to Archimedes’ principle ,
i)Ship ii)Submarine
Suppose ,wt of
in air =W1
Wt. of object in water =W2
؞Upthrust =w1 – w2 (i)
Wt. of beaker
=W3
Wt . of beaker
with displace of liquid =W4
؞ Wt of displace of
liquid =W4 –W3 (ii)
After
calculation the value of (i) and (ii)
W1 – W2 = W4 - W3
Or It show that or verify , Upthrust = Wt. of
displace of liquid or Archimedes’ principle.
Density :-Mass per unit volume is called density. Its S.I.
unit is kg/m3 and C.G.S. unit is
gm/cm3.
Density (d)= Mass(m)/Volume(v)
D = m
Example:- density of water =1000kg/m3 or 1gm/cm3
i)Convert 1000kg /m3
into gm/cm3
= 1000 ×1000 / 100×100×100
= 1gm/cm3
ii)Convert 1gm/cm3
into kg/m3
= 1×100×100×100/ 1000
=1000kg/m3
Relation between density of a body and floatation:-
ii)When the density of an object is less than that of density of the
liquid then object float on the liquid .
iii)When the density of an object is equal to the density of the liquid then the
object floats just inside the surface of the liquid.
Relative density :-(R.D.):-The
ratio of the density of the substance to the density of the water at 4
Relative density (R.D.) =Density
of the substance / Density of substance at 4
Hydrometer and Lactometer :- The instrument which
is used to measure density to liquid is
called hydrometer .It is based on principle law of
floatation.
The instrument which is used to measure density of milk is called lactometer. It is also based on principle of law of floatation .
1.)The gravity of bulb of
hydrometer is made heavier ,why ?
Ans. The heavier bulb of
hydrometer help it to into float up right in stable equilibrium .Therefore the bulb of hydrometer
is made heavier .
2.)The floatation bulb of hydrometer is made
small ,why ?
Ans. The floatation bulb of
hydrometer is made small due to this whole hydrometer does not float on the
denser liquid because denser liquid provides more upthrust.
3.)The stem of hydrometer is marked from top to bottom, why ?
Ans Hydrometer sink deeper in less density of liquid or the length sink portion of hydrometer is inversely
proportional to the density of the liquids .Therefore, the stem of hydrometer
is marked from top to bottom.
Atmospheric pressure:-The pressure exerted by atmospheric air per unit area on surface of earth is called atmospheric pressure. The weight of air itself is the cause of atmospheric pressure. Its S.I. unit is N/m2 or mmHg(millimeter mercury) and measured by help of Barometer.
Barometer .The atmospheric pressure at sea
level i.e. 5N/m2 or 760mmHg, is also
called standard atmospheric pressure.
Atmospheric pressure(p) = d×g×h
Where d=density of air g=
Acceleration due to gravity ,h=depth of air
Air pressure :-The pressure exerted by gas per unit area enclosed in vessel i.e. balloon, is called air pressure .
A simple barometer that is made by help
of mercury and long glass tube is called mercury barometer .It is invented by
the Torricelli .
Construction :-It consist of a narrow glass tube of 100cm
in length ,inverted over a trough containing mercury shown as fig. In mercury
,when mercury level falls inside glass tube then there leaves a blank space is
called Torricellian
vacuum .
Advantages of using mercury in mercury barometer :-
i)It has
density ii) It is silver in color so it can be easily
seen in glass tube. Iii)It does wet glass surface so reading is
accurate .
iv)It does vaporize easily .
Uses of atmospherics
pressure:-
1)It help for movement of air due to
change in atmosphere .
2)We can fill ink inside pen ,medicine
inside syringe ,air inside tube of bus ,car bike etc.
3)Water pump work by help of atmospheric
pressure .
Ans. When we go to higher altitude depth of atmosphere
decreases, so human blood pressure become more
than that of atmospheric pressure due this blood vessel present inside
nose ,ear feel more pressure and rupture .Therefore, when we go to higher
altitude bleeding occurs .
2.)A air filled balloon at
higher altitude brusts ,why ?
Ans. In air
filled balloon at higher altitude ,the atmospheric
pressure become less than that of air pressure inside balloon, so air
filled balloon at higher altitude brusts ,because we know that atmospheric
pressure decreases due increase of height
.
Some practical application of atmospheric pressure :-
1)Syringe :- An instruments that is
used by doctor in hospital to give injection to their patients is called is
syringe .
Construction :-It consist of following following
parts.
i)A piston ii) A barrel iii)A
narrow tube in form of needle
Working :- Working system of syringe
is divided into stokes :-
B)Down stoke:- When piston move downward then, air pressure inside barrel became more than that of blood
pressure so piston of syringe force the liquid inside the body of liquid.
2.)Water pump:- A pump
that is used to takeout underground water is called water pump .It is based on
the principle of atmospheric pressure.
Construction:-It consist of following
parts .
1)Barrel
:-It consist of V2 valve that open during upstroke and closed during
down stroke , outlet and handle
2)Piston :-It consist of V1 valve
that open during down stroke and closed
during upstroke .
3)Metal
pipe :- Its
one end is connected with base of barrel and other end is connected with water
reservoir .
Working :- working system of water pump is divided into two
stokes .
B)Downstroke :-When piston is moved downward then air pressure below piston become more than that of upper portion piston so V2 valve closed and V1 valve open and water piston enter upper portion of piston into the barrel .
3)Air pump :-The that is used to fill up the atmospheric air into the rubber tubes of automobiles ,bicycle etc. is called air pump.
Construction :- It consist of following parts.
1)Piston :- It consist of a hole in upper portion by
which atmospheric air enter inside barrel, and a rubber a downward portion .
2)Piston :-It consist of V1 vale that open
upstroke and closed during down stroke.
3)Rubber pipe:-It consist
of V1 valve that open during down stroke and closed during up
stroke.
Working :- Working system of air pump is divided into two
stroke .
A)Upstroke :-When piston is moved up the pressure below the
piston inside barrel reduce and atmospheric pressure more so V1 vale open and atmospheric
air enter inside barrel and V2 vale closed .
B)Down stroke :- When piston is moved downward air pressure inside
barrel become more than that of air
pressure inside rubber tube so V2
valve open and V1 valve
closed so air inside barrel enter into rubber tube .
Numerical problems
Formula:-
1)P =
2) P=d×g×h
3) U= d×g×h×A
4)F2/F1
= A2/A1
5) d =M/V
6) Wt. of displace of
liquid = Wt of floating body
7) Volume of displace
of liquid =Volume of immersed portion of an object
1)Density of
iron is 7600kg/m3 .What will be the mass of iron block with
dimension of 4cm ×15cm×20cm.
Given,
Volume iron block (v) l×b×h
=4×15×20 =1200cm3 /100×100×100
=0.0012m3
Density of iron (d)=7600kg/m3
Mass of iron block (m) =?
By formula
m=d×v
=7600 ×0.0012
؞m= 9.12 kg
Mass of iron block (m) =9.12 kg
2.)A load of 2000N is be lifted by hydraulic press
whose large piston cylinder has area of cross sectional 4m2. If a
small cylinder has cross sectional of 40cm2 .Calculate the force
necessary to apply on the piston of the small cylinder .
Given
,Load on large cylinder (F2)=2000N
Area of large cylinder (A2) =4m2
Area of small cylinder(A1)=40cm2 = 40/100×100 =0.004m2
Force apply on small cylinder (F1)=?
By formula
F2/F1
=A2/A1
Or 2000/F1
=4/0.004
Or F1= 2000×0.004 /4
F1 =2 N
Force applied on small piston (F1) =2N
3.)Observe the given fig and answer the following
questions .
i)What is pressure exerted on the liquid by the load.
ii)What is pressure acted on X ?
iii)Calculate the area of small cylinder ?
Given,
Force on small piston (F1)=200N
Force on large piston(F2)=12000N
Area of large piston(A2)=2.5m2
i)by formula
P =F2/A2
= 12000/2.5
=4800 pa.
ii)According to pascal’s pressure exerted on large piston equal to
small piston .
؞pressure exerted on piston X=4800 Pa.
iii)by formula
Area of small piston (A1)= A1 ×F1 / F2
=200×2.5/12000
A2 =0.041 m2
Therefore area of small piston (A1)=0.04m2
4.)Piston
A,B;and C are the apparatus given in the diagram are supposed to be
frictionless .What is the area of the piston B? What is force exerted on piston
C?
Given,
Force at piston A (F)=250N
Area of piston A(A)=20cm2
Force at piston B(F)=375N
Area at piston C(A)=10cm2
By formula
Pressure of piston A(P) =F/A
Or P=375/10
Pressure(P)=12.5 Pa
ii)by formula
Area of piston B(A) =F/P
Or A =
؞Area (A)=30 cm2
iii) by formula
Force exerted on piston C(F)=P×A
Or F = 12.5 ×10
؞Fore exerted on piston C (F) = 125 N.
5.) An
iceberg of 50cm×30cm×20cm float on water .The
density of ice berg and water are
900kg/m3 and1000kg/m3 respectively .Calculate the mass of
water displaced and also find out the portion of iceberg that remains above the
water surface .
Given,
Volume of iceberg (v) l×b×h
Or V= 50×30×20
=30000cm3
Or V =0.03 m3
Density of water (d)=10000kg/m3
Density of iceberg (d)= 900kg/m3
Now, i) By formula
Mass of iceberg (m) d×v
Or m= 900 ×0.03
mass of iceberg
(m) 27 kg
we know that .Mass of displaced of
liuid =mass of floating body
or = 27 kg
Therefore mass of displaced of water =27 kg
Again . volume of displaced of water(v)=m/d
Or v=27/1000 =0.027m3
We know that , volume of immersed portion of an object
= volume of displaced of liquid
Therefore, volume of immersed portion of iceberg = 0.027 m3
By formula ,
Immersed portion of an object =Volume of immersed
portion of an object /Total volume of an object
Or immersed portion of iceberg = 0.027/0.03 =9/10= 0.9 parts
Therefore above portion of iceberg = 1- 0.9 =0.1 part
6.) A
rectangular body is completely dipped in water as shown in fig .The upper or
lower surface area it is 2m2.find
the upthrust acted upon it due to water .(density of water is 1000kg/m3).
Given,
Area of body (A)=2m2
Height of given body(h)=h2- h1
Or h= 7-3
=4cm
Density of water (d)=1000kg/m3
Upthrust (U)= ?
By formula
U =d×g×h×A
Or U=1000×9.8×4×2
Therefore (U)= 7800N.
8.)Study
the given diagram and answer the questions .
i)What
is weight of an object in air?
ii)How
much upthrust is exerted by the liquid on the object.
iii)Calculate
the mass of object ?
iv)In
which law this experiment based ?
Ans.
i)By
formula
Weight of object in
air = wt. of object in liquid +wt of displaced of liquid
Or =10+2 = 12N
ii)Upthrust =wt of displaced
of liquid
or =2N
iii)By formula
Mass (m) =w/g
Or m=12/9.8 = 1.22Kg
iV) This experiment based on Archimedes’
principle.
9.)Different weight of a
pieces of stone weighting in three different media air ,water and salt solution
are given below.
|
Media |
Weight |
|
A |
30N |
|
B |
20N |
|
C |
25N |
i)Which of
them are air, water and salt solution .
Ans. Maximum weight is in air
due to minimum upthrust and minimum weight in salt due to maximum upthrust .
So, A=Air B=Salt
solution C= water solution
ii)Find out the mass of water displaced by stone ?
AnsWeight of water
displaced by the stone =30N-25N =5N
Now, Mass o f displaced of water (m) =5/9.8 =0.5 kg
iii)if 1 kg of
stone is equal to 10N ,calculate the mass of stone in air .
Ans. Given,mass of 10 N stone = 1kg
So , “ “ 1N = 1/10kg
Therefore ,mass of 30N =1/10×30 =3kg
10.)Densities of some substances are given in the
table ,answer the following questions on the basis of table.
|
Substances |
Density (gm/cm3) |
|
A |
11 |
|
B |
8 |
|
C |
0.9 |
i)If Mass of all are taken equal which one will have
the largest volume?
Ans. Volume of substance
is inversely proportional to the density of substance So if mass are equal’ Z’
substance will have largest volume due
least density.
ii)If all have equal volume ,which one will have largest
mass ?
Ans.Mass all substances is
directly proportional to the density of substances. So ‘A’ substance will have
largest mass ,due to largest density .
iii) Among the above substance ,which one will float
in water ?
Ans. Among A, B and C substances ,C will float in water because c has less density than that of water .
Unit – 1 Pressure
Group
- A (1 Mark Each )
1. Name the force applied perpendicularly on unit area. [SLC 2070C
2. Define one pascal pressure. [SLC
2070 B. 2067
3.State Archimedes' principle. [SEE
2074 (BC))
4.State Pascal's law.
5.Pressure applied on a liquid enclosed in a vessel will be
transmitted equally in all directions perpendicular to the surface. Which law
is explained by this statement? Name the instrument which works on the basis of
this law? [SLC 2071 E]
6.On what factors liquid pressure depends? [SLC 2070 E, 2068
C]
7.Write three factors that affect liquid pressure kept in
cylindrical tank.
[SLC 2071 E]
8.State Pascal's law and give the name of one instrument based
on it.
[SLC 2072 E, 2071 D, 2070 D, 2069 B, 2066 E, 2065
B&E]
8.On which principle does hydraulic brake base? State this
principle.
[SLC 2072 C, 2070 E]
9.What is relative density? [SLC 2071 D]
10.Name two instruments that are based on the law of floatation. [SEE 2074 (AC)
11. What is hydrometer?[SLC 2071 B, 2070 C, 2069 B, 2067 E]
What is upthrust? [SEE 2074 (DC)]
12.What is lactometer? [SLC 2072 C&E, 2070 A]
13.State the law of floatation. [SLC 2071
B, 2070A, 2069 C, 2067 A,S]
14."The weight of displaced liquid is equal to the weight of
floating object". Which principle does this statement belong to? [SLC 2069 B]
15.What is the effect of density of liquid on the floatation of
an object?
(SLC 2069 C]
16.What is density? [SLC 2068 D]
17.Write the formula based on Pascal's Law. [SLC 2068 D]
18.Weight of an object is decreased when immersed in water,
which law does this statement represent? [SLC 2072 E,
2069 5, 2067 C]
19.What is hydraulic press ?[SLC 2069 E]
20.Write the relation between upthrust and volume of displaced
liquid.[SLC 2069 E]
21.What is the relation between upthrust and the density of liquid
? [SLC 2071 A, 2068 A]
22."Liquid transmits the pressure equally in all
direction.' Which law does this statement represent ? [SLC 2063 El
23.On which law is the working of hydrometer based ? [SLC 2071 D, 2063 B]
24.State law of flotation. Name a device based on that law.[SLC
2070 B, 2069 A, 2066 A, 2057 B]
24.State Archemedes' principle. SEE
2074 (BC), SLC 2072 E, 2068 B, 2066 D, 2063 E
25. Write down the relation of density of
the liquid and its upthrust. [SLC 2062 E]
26.What is upthrust due to liquid ? [SLC ,
2071 C&D, 2061 D, 2059 B]
27.What is the relation of pressure of a liquid with its density
and depth ?
[SLC 2061 A, 2058 C]
28.What two works can be done with a hydrometer? [SLC 2060 A]
29.Name three factors that affect liquid pressure. [SLC 2061 C, 2059 E
30.Mention two factors which affect pressure due to liquid
contained in a vessel.[SLC 2057 E]
Group-B (2 Marks Each )
1.Studs are made on the sole of football players' shoes, why?[SLC 2069 S
2.A drum completely filled with water is taken from earth to
lunar surface. What change in pressure, given by water, at the base of drum
takes place ? Explain with reason. [SLC 2072C]
3.Why does the shape of a vessel not affect the liquid pressure? [SLC 2070 D]
4.The water tank is kept at some height, why ?ISLC 2071 B]
5.The bucket is filled slower in the tap of top storey than that
of down storey, give reason. [SLC 2070 C]
6.The size of air bubble becomes bigger as it rises up in the
water, why?
[SLC 2068 ]
7.What is the relationship between the density of a liquid and
its upthrust? Explain.
[SEE 2074 (CC))
8.Write any two differences between density and relative
density.
[SLC 2072 C, 2069 D, 2068 51)
9.In the given figure, on which surface more pressure is exerted
and why ?
[SLC 2065 D&E]
10.An iron nail (ball) sinks in the water but a ship made up of
iron floats, why? (SLC 2071 C, 2068 E, 2067 EL ).
11.If a hydrometer is immersed in sugar solution and in pure
water, in which it immerse more? Why? [SLC 2068 )
12. Write the difference in floatation of
lactometer in pure milk and sugar dissolved milk.[SLC 2069 ]
13.What is the difference between the immersion of hydrometer in
pure water and salty water? [SLC 2069 A]
14.An iron nail sinks in water but floats in mercury, why?[SLC 2072 C]
15.Write two conditions for a substance to float on liquid.[SLC 2071 E]
16.What difference will you get from the flying of air filled
balloon and the hydrogen filled balloon? [SLC 2069 C]
17.Why is it easier to lift a heavy stone under water than in air
?[SLC 2071 D]
18.It is easier to lift a heavy stone inside the water than air,
why? [SLC 2072E]
19.One feels difficult to breathe in the deep well while cleaning
it, why?
[SLC 2069 C]
20.Speed of flow of water from tap of upper floor is less than
that from the tap of down floor, why? [SLC 2063 E]
21.What is change in pressure at the bottom of a drum filled
with water if it is brought to Himalaya from Terai? Write with reason. [SLC 2063 A]
22.One of the two ladies with the same weight is wearing
pointed-heeled shoes and the other wearing flat shoes.
23.Explain which one exerts more pressure on the ground.
24.It is easier to lift a heavy stone under water, why? (SLC
2066 C]
25.Lifting a stone in water is felt to be comparatively lighter,
why? [SLC 2069 E]
26.The ice made of water floats on water, why? [SLC 2065E)
27.A heavy bulb is made at the base of a hydrometer, why? [SLC 2071 B. 2065 C]
28.The weight of any object decreases inside water. Give reason.
How much weight will an object lose in water ? [SLC
2066 D
29.What will be the effect in the weight of displaced water if
load is added into the ship floating in the ocean ? Write with reason. [SLC 2065 B]
30.The bottom of the wall in a dam is made comparatively
thicker, why?
[SLC 2066 B]
31.A ship coming from sea enters the river, will its hull sink
more or less in river water ? Give reason. [SLC 2066 E]
32.How much water, a girl weighing 450 N, should displace in
order to float in water? Why? [SLC 2060 B]
33.Although a ship is made up of iron, it can float on water,
why?[SLC 2058 E
34.A man exerts more pressure under his foot when he stands with
one foot than when he stands on two feet, why? [SLC 2057 S
35.Bucket of water is filled faster in the downstair tap than
the bucket in the upstair tap. Why? (SLC 2057 C]
Group - C
(3 Marks Each )
1.If the pressure, force and area are P, F and A respectively,
then prove that : P= F/A
2.Prove the relation of pressure exerted by an object with its
surface area and the applied force. (SLC 2069 B1)
3.Prove the relation of pressure exerted by the liquid column
with its height, density and acceleration due to gravity of that place.[SLC
2070 A, 2069 E)
3.Prove that liquid pressure is directly proportional to the
depth of liquid.
[SLC 2072E]
4.Prove that the hydraulic press is force multiplier. [SLC 2072 C, 2070E]
5.An effort of 100N can raise a load of 2000N in a hydraulic
press. Calculate the cross-sectional area of a small piston in it. The
cross-sectional area of a large piston is 4m2. Write any one
application of hydraulic press. (Ans: 0.2m) [SEE 2074 (CC)]
Unit
- Test
Unit 2: Pressure
(चाप) Time: 40 min. F.M.:
22
सबै प्रश्नहरूको
उत्तर
दिनुहोस्
।
(Answer all the questions.)
समूह 'क' (Group
'A') 1x6 =6
1.Name the two factors on which the pressure exerted by a body depends?
2.What is hydraulic press?
3.Name any two instruments based on Archimedes' principle.
4.Define one pascal pressure.
5.What is barometer
6."The weight of displaced liquid is equal to the weight of
floating object". Which principle does this statement belong to?
समूह 'ख' (Group 'B') 3x2=6
7.An iron nail sinks in water but a ship made up of iron floats.
Why?
8.What is the relationship between the density of a liquid and
its upthrust? Explain.
9.Write any two differences between density and relative
density.
समूह 'ग' (Group 'C') 2x 3
=6
10.If the pressure, force and
area are P, F and A respectively, then prove that : P= F/A
11..Prove that liquid pressure is directly proportional to the
depth of liquid.
समूह 'घ' (Group
'D') 1x 4 =4
12.State Pascal's law. .An effort of 100N can raise a
load of 2000N in a hydraulic press. Calculate the cross-sectional area of a
small piston in it. The cross-sectional area of a large piston is 4m2.
Write any one application of hydraulic press.
The
End
Unit -3 Energy
Energy:- The capacity of doing work is called energy .Its
S.I.unit is joule (J) and C.G.S. unit is Calorie (cal).
Source of energy:- The sources through which energy can be produced are called source of
energy
Energy:- The capacity of doing work is called energy .Its
S.I.unit is joule (J) and C.G.S. unit is Calorie (cal).Source of energy:- The sources through which energy can be produced are called source of
energy
Types of energy :- a)On the basis of nature :-They are two type
1.)Primary source of
energy :- The source of energy which can be used in the form in
which they occurs in nature are called primary source of energy .For example : wood ,coal, natural gas ,solar energy etc.
2.) Secondary source of energy :- The source of energy which are
derived from
primary source of energy are called secondary source of energy . For example :bio gas ,hydro electricity
,petrol,diesel,kerosene.etc.
b) on the basis of
nature .- They are two types.
1.)Renewable source of energy:- The source of energy which are produced continuously
in nature and can be used again and
again are called renewable source of energy .Such types of source energy are never
depleted .For example : solar energy ,hydro
electricity, wind energy ,bio mass energy, gobar gas or biogas ,wind energy, tidal energy,
geothermal energy etc.
2.) Non-renewable source of energy :- The source of energy which gets depleted(can reduce) and can not be used again and again are called non renewable source of energy .such types of source energy has limited stock in nature .For example: coal, fossil fuel(mineral oil ) and natural gas. etc.
Some renewable source of
energy :-
1.)Solar energy:- The energy produced by the is called solar energy .The sun is also considered as ultimate or major source of energy ,because all source of energy present on the surface of earth directly or indirectly depend on the energy released by the sun .For example :Hydro electricity is called outcome of solar energy ,because for hydroelectricity stock of water is required ,for water stock water cycle is required and for water cycle sun energy is required .
Process of formation of solar energy:-In sun 27×1023kw energy released per second by thermo nuclear fusion reaction. In which 1.4kw solar energy is received by the surface of earth per square meter
. During
thermo nuclear fusion reaction in sun following given reaction involved inside
it.
Where 1 H1 = Free proton or protium , 1H2 =deuterium , 2He3 =Light helium or
tritium, 2He4
Helium , 1e0 = Positron
In this reaction the mass of 2He4 is less
than that of 4 nuclei of free proton of hydrogen. The loss of mass
according to E=mc2is converted into
light and heat energy .
Conditions requires for
thermonuclear fusion reaction in sun to produces energy :-
1)Very high temperature is required in
the for formation of free proton or protium.
2)Very high pressure is required in the
sun for fusion of free proton.
3.)The sufficient amount of
hydrogen atom is required in the sun for formation of free proton .
4)The sufficient amount of helium
formation is required to produce large amount energy .
Advantages of solar energy :-
1)It is
renewable source of energy and can be used again and again .
2)It can be
used as alternative source of energy .
3)It help to
us protect from energy crisis in future .
4)It is a
pollution free source of energy .
2.) Hydro electricity:-The electricity generated by
rotating turbine with help of water is called hydro electricity .The estimated
capacity of our country is about 83000 mega watt ,but present production capacity
of our country is about 1000 mega watt . It is
second water richest country and most area of this country provided with
mountains or inclined surface .
Causes of possibility of more production of hydro electricity in
Nepal:-
1.)It is second water richest water country .
2)Most of area of this country provided
with mountains or inclined surface .
Causes of difficulties to produce hydro electricity in Nepal:-
1)Lack of money 2) Lack of manpower
Advantages of hydro electricity :-
1) 1)It is
renewable source of energy and can be used again and again .2)It can be used as
alternative source of energy .
3)It help to
us protect from energy crisis in future .
4)It is a
pollution free source of energy .
5)It is easy
to transmit and use .
6)In long term
basis ,it is cheaper than that of other source of energy .
7)It is used
to run T.V. ,Radio, computer ,industries, etc.
3.)Bio-mass energy:-The energy
obtained by burning bio-mass is bio-mass energy .
Bio-mass :- The
pieces made by the compression of raw
dust(wood),fragments of straw, chaff (husk after threshing), with
help of machine is called bio-mass .
Advantages of bio-mass energy:-
1) 1)It is
renewable source of energy and can be used again and again .2)It can be used as
alternative source of energy .
3)It help to
us protect from energy crisis in future .
4)It is used
for cooking food and other human activities.
4.)Bio-gas or Gobar gas :- Mixture of methane ie 60%,carbondioxide ie.40% hydrogen sulphide is called bio-gas .
It is produced by decomposition of
animal wastes ie.dung in presence of water due to anaerobic bacteria in the
bio- gas plant.
1) 1)It is renewable source of energy and can be
used again and again .2)It can be used as alternative source of energy .
3)It help to
us protect from energy crisis in future .
4)It produce
more heat while burning easily.
5)Due to
agriculture country ,waste materials for this gas easily available in our
country.
6)It is used
for cooking food ,burning light etc.
5.)Tidal energy :-The
energy which is generated with help of tides of sea is called tidal energy .For
example : hydro –electricity is generated from tides of sea by rotating turbine
.
Process to generate hydro- electricity from tidal energy :-In those area where tides
comes, big dams are constructed at sea shore
near water .When tides comes up in sea then water enter into dams by crossing
dams and water is trapped in the dam, then water
is again passed toward sea through pipes .which is used to rotates turbine and then generator for produce electricity .
Advantages of tidal energy :-
1) 1)It is
renewable source of energy and can be used again and again .2)It can be used as
alternative source of energy .
3)It help to
us protect from energy crisis in future .
4) It is used
to produce large amount hydro- electricity .
6.)Wind
energy:- The energy obtained from blowing wind is called wind
energy .For example: Electricity is generated from wind energy by rotating
generator ,it is used to operate wind mill, to pump up underground water, to
sailing boat .
Process to generate hydro- electricity from wind energy :-
In those area
where wind blow in a high velocity .At first fan having
large blades are run with the help of blowing air ,then generator is
run by help of fan for produce
electricity .
Advantages of wind energy :-
1) 1)It is
renewable source of energy and can be used again and again .2)It can be used as
alternative source of energy .
3)It help to
us protect from energy crisis in future .
4) It is used
to produce large amount electricity ,to
operate wind mill, to sailing boat ,to pump up under ground water.
7.)Geothermal energy :-The heat energy obtained from interior part of earth
is called geothermal energy .In our country of several places ie. Tato pani
is the example of geothermal energy ,it is also obtained by some natural
disaster ie .big earth quake , volcano eruption.
Process to generate electricity from geothermal energy :-
To produce
electricity from geothermal energy ,at first in such places two holes are drilled into the earth, through which
metal pipes are put into them ,then cold water is pumped from one end and cold water change into steam due to heat of rocks then
comes out from other pipe ,then by help steam ,steam engine is run and then
generator for produce electricity .
Advantages of geothermal
energy :-
1) 1)It is
renewable source of energy and can be used again and again .2)It can be used as
alternative source of energy .
3)It help to us protect from energy crisis in future .
8.)Nuclear energy :-The
energy produced from nuclear reaction in nuclear power plant is nuclear energy
.Nuclear energy are produced by two methods, in
both methods some mosses is lost during reaction
and loss of mass according to E=mc2 is
converted into light and heat energy .Which is used to boil water ,to
run the steam engine and to generate electricity .
i)Thermo-nuclear fusion reaction :- The nuclear reaction in
which two light nuclei ie. Hydrogen combine to form
heavy nuclei ie. Helium with liberation of large amount heat and light
energy is called thermo nuclear fusion reaction .In this reaction large amount heat and light is produced than that fission
reaction ,high pressure and high temperature is
required ,it is not chain reaction .For
example : the energy produced from sun and hydrogen are
based on the fusion reaction .
ii)Thermo-nuclear
fission reaction:- The nuclear reaction in which an unstable nucleus of
heavy atom ie.uraniun-235 split up into two medium size
of nuclei ie. Barium and krypton with liberation of large amount heat
and light energy is called thermo nuclear fission reaction .In this reaction less amount of light and heat energy is produced than that of
fusion reaction ,it is chain reaction ,high
pressure and high temperature is not required .This reaction is carried
out by bombarding the heavy nuclei with neutrons. For
example :Atom bomb is based on fission
reaction .
Fossil fuel:-The fuel which is obtained from fossil of dead plants
and animals found in sedimentary rocks is called fossil fuel .For example : Coal ,mineral oil ie. Petrol ,diesel ,kerosene,
natural gas etc.
Fossil fuel energy :-The energy which
are obtained by burning fossil fuel is energy.
Coal:- The fossil fuel which are formed by modification of fossil of plant due to high temperature and high pressure under the is called coal or fossil fuel. .it is found in sedimentary rocks .
i)It is used
as fuel in different industries and factories .
ii)It is used
for cooking ,heating ,and run steam engines.
iii)It is used
for manufacturing many drugs ,fertilizers, plastics, synthetic fibers, bricks.
Minerals oil:-The fuel which are formed by fossils of plants and animals under high pressure and high temperature and obtained from minerals are called mineral oil .For example: petrol, diesel ,kerosene etc.
Uses of mineral oil:
i)It is to produce heat and electricity .
iii)It is used
in transportation.
Charcoal:- The coal
which are formed by heating the wood in the absence of air by artificial
method is called charcoal .It is used to
produce heat .
Advantages of fossil
fuel ie coal, mineral oil ,Natural gas :-
1)It is cheaper and more easy to supply
than other types of fuels .
2) It can be easily transmitted .
3)It is used to run vehicles and machine
in industries .
4)It is used as source of heat and also
used to generating electricity .
Alternative source of energy :- The source of energy which are used to replace or preserve non renewable or conventional source of energy are called alternative source of energy of energy .For example: in context of Nepal ie .Hydro electricity ,gobar gas ,bio- mass ,solar energy ,and other wind energy , tidal energy, geothermal energy ,nuclear energy .
Energy crisis :- The shortage of non-renewable source of energy on
the earth is called energy crisis .
Causes of energy crisis or facing of energy problem in near future :-
1)High demand of source of energy due to growth of population .
2)Over uses
of non renewable source of energy .
3) Lack of development and use of alternative
or renewable source of energy .
4)The earth contains only limited stock of non renewable source of energy .
5)Urbanization
and industrialization .
Methods for solving energy crisis :-
1)By development and use of alternative source of
energy to replace the non renewable source of energy .
2)By conserving and avoiding unnecessary use of non
renewable of source of energy .
3)By the development and use of device which can be
operated by renewable source of energy .
4)By controlling growth of population and urbanization
which are increasing day per day .
Present status of energy
consumption in the world :-
Source of energy Consumption(%)
i)Mineral oil = 37%
ii)Coal = 27%
iii)Naturalgas =
14%
iv)Bio-fuel = 14%
v)Hydro-electricity = 5%
vi)Nuclear
energy = 3%
Total =
100%
Einsteins’s mass ,energy relation:- Einsteins’s said that mass and energy are equivalent or when destroyed during nuclear
reaction change into energy .so he related mass
and energy by the equation
E=mc2
where E= energy, m= mass Destroyed during nuclear reaction , c= velocity of light (3×108m/s).
Unit –
3 Energy
Group -A
(1 Mark Each)
1.What is primary source of energy? (SLC 2068 S]
2.What are the types of energy sources based on time of
replacement ? Write down their names [SEE 2074 (CC)
3.Define renewable source of energy. ISLC
2071 B, 2070 A, 2068
4.What is renewable energy? [SLC 2065E]
5.Give any two examples of non-renewable source of energy
6. What type of energy is coal ? [SLC 2068A)
7.What is hydro-power ? [SLC 2071A)
8.Name any one renewable
energy. [SLC 2072E)
9.For what two natural processes is the solar energy being used?[SLC
2070 C]
10What is bio-fuel ?[SLC 2068 E
11. What amount of average solar energy does the earth surface
receive per square meter? (Ans: 1.4 kW/s)[SLC 2069 B]
12.What is nuclear fuel?[SLC 2072 FW, 2070 E, 2067 B]
13. Write the name of any two radioactive
elements. (Ans: Uranium, Plutonium) [SLC 2069 A, 2069 S]
14.What is energy crisis ?[SEE 2074 (DC), SLC 2072 FW]
15.What is the source of solar energy ?-
[SLC 2070 E, 2069 E]
16.What is fossil fuel ? [SLC 2070S, 2068
B, 2063 B]
17. Write a major disadvantage of fossil fuel.[SLC
2069 C]
18.What is geothermal energy ?[SLC 2067 S, 2063 C
19. Write any two natural phenomena from
which geothermal energy can be obtained.[SLC 2069 B]
20.What is nuclear fusion ?[SLC 2070 B, 2066, 2062 E, 2061 D, 2058
A)
21.Define nuclear reaction that takes place in the Sun.[SEE
2074(AC)]
22.What is nuclear fission? [SLC 2071 C]
23.Name any two main sources of energy used in world. [SLC 2062 B]
24.What is alternative source of energy? [SEE 2074 (BC), SLC 2061 E]
25.Give any two examples of alternative source of energy.
[SLC 2061 E]
26.What is thermonuclear fusion reaction ? Write down a cause of
energy crisis.
[SLC 2072 E, 2070 A, 2066 A, 2061 B, 2057 S]
27.What are renewable and non-renewable sources of energy ? [SLC 2060 S]
28. What is the 'alternative source of energy'? [SLC 2072 C, 2060 E]
29.Write one main reason that may cause the possibility of energy crisis
in future.[SLC 2059 E]
30.What type of energy sources are referred as "Alternative
energy sources" ?[SLC 2059 B, 2058 D]
31.List two renewable sources of energy. [SLC 2057 E]
Group- B (2 Marks
Each )
1.Write two differences between renewable and non-renewable
sources of energy. [SLC 2065 A, 20595.
2.Why is hydroelectricity called renewable source of
energy? [SLC 20615]
3.Fossil fuel is known as non-renewable source of energy, why (SLC 2066 C]
4.Why is the use of wood as a fuel not advised although forests
can be replenished?
[SEE 20741 )
5.Differentiate between thermonuclear fission and fusion. (SLC 2071 B&D, 2070 D, 2068D, 2067
6.Coal and petroleum are known as non-renewable sources of
energy, why? [SLC 2065 C]
7.State any two causes of energy crisis. [SLC
2065 C]
8.'Energy crisis may occur in the world in near future.' Write
two reasons to justify this statement. (SEE 2074 (DC)
9.Which of the following are non-renewable sources of energy:
mineral oil, hydroelectricity, tidal energy and coal ?[SLC
2072 )
10.Write two reasons to encourage the farmers by Government of
Nepal to establish biogas plant. (SEE 2074 (CC)]
11.The higher priority has been given for the use of biogas energy in Nepal. Give two reasons. (SLC 2069 B, 2069 S]
12.Give any two reasons that the sun is considered as the main
source of energy.[SLC 2067 C]
13.Justify with two reasons that the hydroelectricity is the
best alternative source of energy in the context of Nepal. [SLC 2072C, 2065 E]
14.In the present world, the use of hydroelectricity is
increasing. Write any two reasons. [SEE 2074
(AC), SLC 2070 D]
15.The use of alternative source of energy helps to control the
energy crisis, how? - [SLC 2062 C]
16."Nepal has high potentiality of producing
hydroelectricity". Prove this statement with two reasons. (SLC 2060 D]
17..Show the difference between nuclear fusion and nuclear
fission with an example of each. (SLC 2059 A]
18..Write two causes that Nepal Government has given higher
priority for the production of hydroelectricity.[SLC 2066 E]
Group
- C
(3 marks Each )
1.In fact the hydroelectricity is an indirect source of solar energy.
Clarify this statement. We might face energy crisis in near
future. Why? [SLC 2069 C, 2067 A]
2.Government of Nepal encourages the farmers to establish
bio-gas plant. Write any two scientific reasons of it. In the context of Nepal,
it is better to use energy like solar power. Justify your answer with two
reasons. [SLC 2070S, 2068D, 2069 A, 2065 B&D]
3."The sun is the main source of energy." Give two
reasons to justify this statement. Suggest any two alternative ways to prevent
the energy crisis in the context of Nepal. [SLC 2063 A]
4.In the context of Nepal both bio-fuel and solar energy are
useful out of these two sources of energy, which one will be more useful ?
Justify your answer with two reasons. [SLC 2071 D]
Group-
D (4marks Each )
1.Briefly describe how energy is produced in the sun. List any
four alternative sources of energy that are relevant to Nepal.[SLC
2063 D]
2.How is nuclear energy produced ? Nepal has high potentiality
for producing hydroelectricity however difficult to produce it. Give two
reasons of each.
[SLC 2069 D, 2063 E] 109
3.The government of Nepal has been hiking the price of petroleum
products from time to time. Suggest two ways how hiking the price of petroleum
products helps in pushing the problem of energy crisis further in the future. [SLC 2062 D] 110.
4.Describe the nuclear fusion taking place in the sun with
chemical equation.
[SLC 2060 C]
5.Write down two causes of extreme uses of petrol, although it
is a non-renewable source of energy. Give the equation of process of formation
of helium atom from hydrogen atoms in the sun. [SLC
2060 A]
6.Explain, why there is an acute need of the search for
alternative sources of energy on the earth. (SLC 2059 Dj
7.Nowadays, it is found that government has encouraged to use
the biogas, why?
[SLC 2057 B]
8.Justify giving four reasons that the use of hydropower should
be increased than that of coal and mineral oil for energy. [SLC
2057 A] 115.
9.Why is the development and use of alternative energy sources
necessary in today's world ? Explain.( SIC 2050 R )
Unit - Test
Unit 2: Pressure
(चाप) Time: 40 min. F.M.: 22
सबै प्रश्नहरूको
उत्तर
दिनुहोस्
।
(Answer all the questions.)
समूह 'क' (Group
'A') 1x6 =6
1.What is renewable source of energy?
2.What are two conditions required for nuclear fusion reaction
that takes place in the sun?
3.What is hydroelectricity? What is the estimated hydroelectric
potentiality of Nepal
4. What is nuclear fission reaction?
5.Write
the name of any two radioactive elements
6.What is alternative source of energy?
समूह 'ख' (Group
'B') 3x2=6
7.The sun is considered as an ultimate source of energy. Justify this statement.
8.Write two differences between fossil fuel energy and biofuel.
9.Write two differences between nuclear fusion reaction and
nuclear fission reaction.
समूह 'ग' (Group'C') 2x 3 =6
10.How is nuclear energy produced? Describe in brief.
11.Why should energy be conserved? Mention any three steps, you
would take at home to conserve energy.
समूह 'घ' (Group
'D') 1x4 =4
12.All the sources of energy present on the earth are the
outcomes of solar energy. Justify this statement with examples.
The End
Unit -4 Heat
Heat
:- The sum of kinetic
energy of molecules of an object is called heat . Its S.I. unit is joule and
C.G.S. unit is calorie and measured by calorimeter .It is transmitted from one place to
another place.The quantity heat of present
in an object is directly proportional to their
mass or number of molecules and their kinetic energy
One calorie or one calorie heat :- The amount of heat required to rise the temperature
of 1gm of pure water by 1
1cal =4.2 joule
We know that,
1kg( 1000gm) of water requires to raise the temp by 1
1gm of water
requires to raise the temp by 1
Therefore ,1calorie heat = 4.2 joule.
Effects of heat :-following are the effect of heat .
i)It change the state of matter .
ii)It change the temperature of an object .
iii)It change the size or volume of an object .
iv)It change the solubility of the substance
.
1. )Fig shows the kinetic energy of different molecules. calculate the average kinetic
energy .
Average kinetic energy of
Molecules = 4+5+3+4/4
= 4 joule
The average kinetic energy of molecules of an object is called temperature .Its S.I. unit is is Kelvin (K) and measured by thermometer .It is not transmitted from one place to another place .The temperature of an object is directly proportional to the average kinetic energy molecules .
Thermometer :- The instruments which is used to measure temperature is called thermometer .
Structure of thermometer :-
It consist of long glass tube having a fine capillary tube. The lower end of glass tube
consist of a bulb contains mercury or alcohol as
thermometric liquid .Its outer body consist of a scale is called thermo-metric scale .
Principle of thermometer :- The volume of liquid expands on heating and contract on cooling is know as principle of thermometer
.
Working :-When bulb is kept in contact of hot body then volume of liquid inside the bulb increases ,that the temperature of inside capillary tube by help of thermo-metric scale .
Thermometric
liquid :-The liquids
which is filled in the bulb of thermometer to measure temperature are
called thermo metrics liquid .They are :
1)Mercury :- Causes used as thermo metric liquid :-
i)Mercury is good conductor of heat .
ii)It is shiny and opaque .
iii)It is does not stick to the inner wall of capillary tube .
vi)The freezing point of mercury is -39 ℃
2)Alcohol:- Causes used as thermo metric liquid :-
i)It Is good conductor of heat .
ii) It is does not stick to the inner wall of capillary tube .
iii) It is cheaper than that of mercury .
iv)Its expansion rate is six times more than that of mercury .
v) vi)The freezing point of alcohol
is -117℃
1.)The boiling temperature of water can not be measured with the
help alcohol thermometer, why?
Ans. we know that ,boiling point alcohol thermometer is 78℃ but water is 100℃ so ,above 78℃ alcohol vaporize and can not give reading thermometer .Therefore ,boiling temperature of water can not be measured by alcohol thermometer .
2.)food is
cooked faster in a pressure cooker than that in an open pot ,why?
Ans. When pressure inside the cooker increase then boiling point of water also increases ,so water boil above 100 ℃ and food is higher temperature therefore ,food cooked fast than that in an open pot , because we know that boiling point is directly proportional to the pressure .
Temperature
scale :-There are 3 major types of temperature scale :
i)Celsius Scale or Degree centigrade
scale(
ii)Degree
Fahrenheit cale (℉
3)Kelvin
scale :-The scale in which lower fixed point is 273K and
upper fixed is 373K is called Kelvin scale . In this scale the range between two points is divided into 100 equal parts and in
Kelvin scale water freeze into ice at 273K and boil at 373 K.
The relation between different temperature scales :-
=C-0/100 =F-32/180 =K-273/100
Types of thermometer :-
There are different types of thermometer :
1)Clinical
thermometer :- A thermometer that is used to measure temperature
of body is called is clinical thermometer .The normal temperature of human body
is 37
Construction :-It consist of two parts ie. Bulb and stem .The bulb is thin walled and filled with mercury .The stem is long and prismatic structure having capillary tube that help to magnify image of capillary tube and make constriction that help to prevent back flow of raised mercury level .The stem of thermometer is calibrated with scale ie 350C 420C in Celsius scale and 94 0C to 108 0 F in Fahrenheit scale.
2)Laboratory thermometer :-The thermometer that is in lab. to measure temperature of materials is called is laboratory thermometer .Its bulb is filled with mercury or alcohol .It has temperature range from -10 0C to1100 C
3)Maximum-minimum thermometer
:- A thermometer that is used to measure
maximum –minimum temperature of 24 hours of
certain place is known as maximum- minimum thermometer .
Construction:- It consist
of U shaped glass tube having bulb on their end .One side measure minimum temperature filled with alcohol and other side
filled partially alcohol and mercury measure maximum
temperature .It consist of two metal index at
two side of tube that indicates max-min temperature .
Working :- When temperature increases the volume of alcohol increases that push mercury end upward and metal index indicate maximum temperature, when temperature fall volume of alcohol contract and mercury push alcohol side of metal index other end upward that indicate minimum temperature .later small magnet is used to return metal index again to the surface of mercury .
Specific heat
capacity (SHC):- The amount
heat required to the temperature of 1kg of masses by 1
For example : specific heat capacity
of water is 4200j/kg
1.)Study the given table answer the
question .
|
Substance(metal) |
Specific
heat capacity |
|
A |
900j/kg |
|
B |
700j/kg |
|
C |
500j/kg |
i)What do you mean by statement that specific heat capacity of B is 700j/kg℃?
Ans. It means that 700j heat is required to raise the temperature of 1kg of B metal by 1℃ .
ii)If equal
amount of heat is given to equal mass of substance .Which one of given substances will gain more temperature and
which one of substance will gain low temperature ?
Ans.The substance C will
gain more temperature and substance A will gain low temperature because
C metal have lowest and A have highest
specific heat capacity .
iii)If equal mass of substance at 2
Ans. A
metal will make the deepest hole in the wax slab ,because the specific heat
capacity of A metal is the highest .
2.)Why water
is used to cool the engine of vehicle ?
Ans. Water
has highest specific heat capacity so it help to keep engine cool for long time
.Therefore water is used to cool engine of vehicle .
3.)Water is
used in hot water bag not other liquid
,why?
Ans. Water has highest specific heat capacity
so, it help to keep warm body for long time .Therefore ,water is used in hot
water bag .,
4.)In desert ,it is very hot during day and it is very
cold during night ,why?
Ans. The surface of
desert consist of sand which has very low specific heat capacity so, sand gain
heat very quickly during day and loss heat very quickly during night .Therefore
,it is very hot during day and very cold during night .
Q = m×s×dt or t (i)
Where Q =Amount of heat lost or gained ,m =
mass of an object , s = specific heat
capacity , dt =change in temperature , t= Temperature
Prove that Q =
m×s×dt
Suppose, A body of mass m is heated to increase its temperature
from t1
According to heat law
Heat loss or gained by a body is
directly proportional to the mass of a
body and change in a temperature .
Q∝
Q
Combining eqn (i) and eqn (ii)
Q
1 Joule heat :- The amount of
heat required to raise the temperature
by 1℃ of an object having mass 1 kg and specific
heat capacity 1j/kg℃
1 joule heat =1kg ×1j/kg℃ × 1
Calorimetry :-The measurement of heat lost or gained by an
object is called calorimetry .
Principle of
calorimetry :-It states that, When a hot body
is mixed with cold body ,the heat lost by hot
body is equal to heat gained by cold body . ie
Heat lost by hot body = Heat gained by cold body
Principle of thermal
equilibrium :- It state that Heat
always flow from higher temperature to lower temperature until the temperature
of heat donor and heat receiver become equal .in short equation is given :
m1s1(t1- t) =m2s2(t – t2) 一 (i)
Where,m1 = mass of 1st body
,s1 = Specific heat
capacity of 1st body ,
t1 = temperature of 1st body
m2 = mass of 2nd
body , s2 =s Specific heat capacity of 2nd body ,
t2 =temperature of 2nd
body, t = final temperature .
1.)During high fever , wet clothes is kept on the forehead of the
patient ,why ?
Ans.
A wet clothe is kept on the forehead of patient having high fever
to absorb more heat from the head and water evaporates .It help to reduce high
temperature of patient because we know that heat always flow from high temperature
to low temperature .
2.)Some time ,tight bottle
metal cap is dipped into hot water to open it ,why?.
Ans.
When tight bottle metal
cap is dipped into hot water ,there will be
unequal expansion ie. Cap expand before than that of glass so metal cap
become lose and open easily .
3.)Water in the earthen pot remains cold in summer ,why ?
Ans. The earthen pot has so many pores on it .When water is heated inside and hot water oozes out (leakage slowly) through the pores into the atmosphere so cold water only remains inside the pot .Therefore ,water cool inside the earthen pot .
4.)Why do we sweat in summer ?
Ans. In summer, the atmospheric temperature goes up higher than that of our normal body temperature ie .37℃ , so to maintain our body temperature ie 37℃ our body losses excesses heat by sweating .
i) Q
= m×s×dt or t
ii) m1s1 (t1 – t) = m2s2(t –t2)
Note :-
-Specific heat capacity of water =4200j/kg℃
-
Normal temperature of water ,highest
density of water ,lowest
volume of water =4.℃
-highest volume ,lowest density of water =0℃
1.)2.1×105j of heat energy is required for 2kg of water to raise its temperature from 25℃ to 50℃. Find the specific heat capacity of water .
Given,
Amount of heat (Q)=2.1×105 j
=210000j
Maas (m)= 5kg
Change in temperature(dt)=50℃ -25℃ =25℃
Specific heat capacity (s) =?
By formula
Q = m×s×dt
Or 21000 = 5×s×25
Or s= 210000/5x25= 4200
Therefore ,Specific heat capacity (S) =4200 j/kg℃.
Ans.Given,
Mass of water
(m)= 2kg
Amount of heat
(Q) = 8400j
Initial
temperature (t1) =10
Raise in temperature
(t)=?
Final
temperature (t2)= ?
By
formula
Q =m×s×t
Or 8400 =2×4200×t
Or t = 84000/4200x2 =10
Therefore ,raise of temperature (t) =10
Again ,Final temperature (t2)=t1
+ t
Final temperature (t2) = 10 +10
=
20
3.)A
beaker contains 0.2kg of water at 20
Given ,
Mass 1st body (m1)
=0.2kg
Specific heat capacity of 1st
body (s1) =4200j/kg
Temperature of 1st body (t1)
=20
Again ,Mass of 2nd body (m2)=0.3kg
Specific heat capacity of 2nd
body(s2)=4200j/kg
Temperature of 2nd body (t2)
=60
Final temperature (t) =?
By formula
m1s1(t1
–t ) =m2s2(t –t2)
or 0.2 ×4200(20-t ) =0.3×4200(t- 60)
or 840(20-t) =1260 (t-60)
or 16800-840t =1260t-75600
or 2100t =92400
or t = 92400/2100
=44
Therefore final temperature (t)=44
Unit - 4 Heat
Lens :- A transparent refracting medium bounded by two spherical a spherical surface is called lens
1)Convex lens:- i)The lens which is thicker in middle and thinner in edge is called convex lens .
ii)It converge parallel beam of light after refraction so it is also called converging lens. It help burn paper due to its converging properties.
Iii) The power of convex lens +Dioptre (D) because it has positive focal length due to its real focus .
iv)It form the real and inverted image when the object is placed further from the lens and virtual image when object is placed between focus and optical center .
2.)Concave lens :- i)The which is thinner middle and thicker in edge is called concave lens .
ii)It diverge the parallel beam of light after refraction so it also called diverging lens .
iii)The power of concave lens is – Dioptre (D) because it has negative focal length due to its virtual image .
iv)It form always virtual and erect image .
Image:_When light ray coming from object falls on lens and get refracted ,then refracting rays produce a picture is called image is
Called image .They are two types :
i)Real image:- The image which can be obtained on the screen is called real image .It is always inverted .
ii)Virtual image:-The image which can not be obtained on the screen is called virtual image .It is always erect.
Uses of convex lens:-
i)It is used as magnifying lens.
ii)It is used in optical instrumentie.ie. Hand lens ,microscope ,telescope etc.
iii)It is used to burn paper due to its converging properties .
iv)It is used to correct long sightedness of defect of vision.
Uses of concave lens:-It is used to correct short sightedness of defect of vision.
Parts of lens :-
i)Principle axis :- The line passing through optical centre is called principle axis .It is denoted by P.
ii)Optical centre :-The central point of the lens is known as optical centre .It is denoted by small c and any distance are also measured from the optical centre in the lens .
iii)Principle focus :- The point where the ray of light parallel to the principle axis converge or diverge after refraction is called principle focus .It is denoted by F.
iv)Focal length :- The distance between the principle focus(F) and optical centre(c) is called focal length .It is denoted by f.
v)Centre of curvature :- The centre of spherical surface from which the lens has been cut is called centre of curvature .It is denoted by capital C . A lens has two spherical surface or centre of curvature .
vi)2F:- Double distance of F is known as 2F .
Rules for drawing ray diagram and image formed by convex and concave lens . :-
i)The ray parallel to principle axis passes through the principle focus after refraction ,but incase of concave lens the rays appear to be diverging from principle focus .
ii)The ray passing through optical centre goes straight .
iii)The image is formed at that point , where these rays cut
eachother.
Position of objet and image is formed by convex lens :-
i)When object is placed at 2F =The image is formed at 2F on the other side of the lens .
ii)When object is placed beyond 2F. =The image is formed between F and 2F other side of lens .
iii)When object placed between F and 2F = The image formed beyond 2F other side of lens .
vi)When object is placed at F = The image formed at infinity (
v) When object is at infinity (
iv) When object is kept between principle focus (F) and optical centre (C) = The image is formed beyond object virtual, erect and larger on the same side of object .
1.)Draw neat and labeled ray diagram showing image and also write down the characteristics of the the image are formed by convex lens .When object is placed …
i) Object at 2F:-
Na Nature or characteristics of image :-
i)The image is formed at 2f on the other side of lens .
ii) The is real and inverted .
iii)The size of image is same to the size of object .
Uses :-The types of image is used in terrestrial telescope .
Ii)Object at beyond 2F:-
Nature or characteristics of image :-
i)The image is formed between F and 2F on the other side of the lens.
Ii)The image is real and inverted .
iii)The size of image is smaller or diminished than that of object .
Uses :-
I)This types of image is used in photographic camera .
iii)Object between F and 2F :-
Nature or characteristics of image :-
i)The is formed beyond 2F on the other side of lens .
ii)The size of the image is larger or highly magnified than that of object .
iii)The image is real and inverted .
Uses i)This types of image is used in film projector, slide projector
iV)Object at F :-
Nature or characteristics of image :-
i)The image is at infinity (∞
ii) The size of image is larger or highly magnified that of object .
iii)The image is real and inverted .
Uses i)This types of image is used in the search light .
v)Object at infinity (∞
Nature or characteristics of image :-
i)The image is formed at 2F .
ii)The image is real and inverted .
iii)The size of image is smaller or diminished than that of object .
Uses :- i)This types of image is used in the telescope .
vi)Object between F and C :-
Nature Or characteristics of image :-
i)The image is formed beyond object at same side of the lens .
ii)The size image is larger or highly magnified than that of object .
iii)The is real and inverted .
Uses This types of image is used in the hand glass or simple microscope .
The position of object and image is formed by concave lens :-
i)When object is placed at 2F =
ii)When object is placed beyond 2F=
iii)When object is placed between F and 2F=
iv)When object is placed at F =
v)When object is placed at infinity(
vi)When object is placed between F and C=
Nature or features of image :
i)The image is formed that of between optical centre(C)and focus(F)on same side of the lens.
ii)The image is virtual and erct .
iii) The is smaller than object.
Uses :-
i)This types of image is in the spectacles for correction of short sightedness .
1.)Draw neat and labeled ray diagram showing image and also write down the characteristics of the the image are formed by concave lens .When object is placed …
i) Object at 2F :-
Nature or characteristics of image
i)The image is formed between F and C at the same side of the lens .
ii)The size of image is smaller than that of object .
iii)The image is virtual and erect .
Uses:-
i)This types of image is in the spectacles for correction of short sightedness
ii) Object at infinity
Nature and characteristics of image :-
i)The image is formed between F and C at the same side of the lens .
ii)The size of image is smaller than that of object .
iii)The image is virtual and erect .
Uses:-
i)This types of image is in the spectacles for correction of short sightedness
Power of lens :-Ability of lens to converge or diverge the ray of light is called power of lens .Its S.I. unit is Dioptre (D).
Power of lens (P) =1/f (meter) Where f = focal length
One dioptre power :-The power of lens having 1 meter focal length is called one dioptre power .
Magnification :-The ratio of image distance (v) to object distance(o) is called magnification .It have no unit .
Magnification(M)=image distance (v) /Object distance (u)
Or Image height (I) /Object height (O)
Note:-i)if m>1 then image greater then object.
ii) if m=1 then image is equal to object .
iii)if m<1 then image smaller than object.
Relation between image distance(v),object distance (u),and focal length (f):-
1 /f = 1/u +1/v Where f = focal length , u = object distance
and v = image distance .
Numerical problems :-
i)Power of lens (P) = 1/f(meter)
ii) 1/f =1 /u +1/v
1.)An object is placed at a distance of 6 cm from focal length 4 cm
i)Calculate focal length and nature of image ?
ii)Calculate power and nature of lens ?
iii)Calculate magnification ?
iv)Draw neat and labeled ray diagram showing image formed by convex lens.
Given,
Object distance (u)=6cm
Focal length (f)=4cm
i)by formula
1/f =1 /u +1/v
Or 1 /4 = 1/6 +1/v
Or 1/4 - 1/6 = 1/v
Or 1 /v = 3-2 /12
Or 1/v = 1/12
Therefore ,image distance (v) =12 cm
Nature of image :-
i)The image is real and inverted .
Ii)The size of image is larger than that of object .
iii)The image is formed at 12cm distance on the other side of the lens .
(Note.-If the value of v is +tive the image is real and inverted and formed other side of the object ,but if the value of v is –tive the image is virtual and erect and same side of object.)
ii)by formula
power of lens(P) =1 /f (meter)
or P = 1 /4 /100
Or P = 25 D
Therefore, thepower of lens (P) =25 Dioptre.
The nature of lens is convex because the focal length of lens is +tive .
iii)By formula
Magnification (M)= image distance (v) /object distance (u)
Or M = 12 /6 = 2
Therefore, magnification (M) =2 or size of image is 2 times larger than that of object.
iv)
2.)An object is placed 6 cm from a convex lens of focal length 2cm .
i)Calculate image distance and nature of image .
ii)Calculate power of lens .
iii) Calculate magnification .
iv)Draw neat and labeled ray diagram showing the image formed by convex lens .
3.)An object is placed at distance 2cm from a convex lens of focal length 4 cm .
i)Calculate image distance and nature of image .
ii)Draw neat and labeled ray diagram showing the image formed by convex
4.)A hand lens has 25 D power . Where should the lens be kept to read the letter of book?
Given ,
Power of lens (p) = 25D
Focal length (f) =?
By formula
P =1 /f (meter
Or 25 = 1 /f
Or f = 0.04 m
Therefore ,focal length (f) =0.04 ×100 =4cm
Hence ,the lens should be kept at 4cm for from the book.
Optical instruments :- The instruments which are formed by using lens are called optical instruments .They are 2 types :-
i)The optical instruments which form real image .For example : Camera , film projector , eye etc.
ii)The optical instruments which form virtual image .For example : Hand lens ,microscope ,telescope etc.
Uses of land lens :-i)It is used to repair watch to see small parts by the mechanics .
ii)It is used in the lab. to observe parts of flower ,insect etc .
Eye :-The sense organ which give us sensation of sight is eye .
Sclera : The strong and white color of layer of eye is called sclera . It protect and maintains the shape of eye ball .
Choroid :-The middle layer of eye is choroid .Which is rich in blood vessels
So, it help to supply blood to the retina .
Retina :-The inner most layer of eye is called retina .It acts as a screen in which object of image is formed .
Ciliary muscles .-The muscles in which the lens of eye is attached is called ciliary muscles .It help to change the focal length of lens by contraction and expansion of it .
Iris :- A muscular diaphragm that remains between cornea and lens is called iris .It control the amount of light entering to the eye by changing the diameter of pupil .
Pupil :-The central opening of iris is called pupil . It help to pass light inside the eye .
Cornea :-The transparent protective membrane that covers the front part of eye is called cornea .
Eye lens :-A convex lens made up from transparent material present behind the iris is called eye lens. It form real ,inverted ,and smaller image than that of object .
Vitreous humour and aqueous humour :- The vacant space behind the lens is filled with transparent liquid is called vitreous humour .
The vacant space between cornea and lens filled with transparent liquid is called aqueous humour .Aqueous humour and vitreous humour both help to maintain shape and size of eye ball .
Focusing :-The process of adjusting the distance between the and screen in order to produce image is called focusing . The focusing is done in eye by change the focal length with help of ciliary muscles .
Far point :-The farthest point from the eye which can be seen clearly (
Near point :- The nearest point from the eye which can be seen clearly is known near point .The near point of normal human is 25cm from the eye .
Defect of vision :-When the lens of can not change its focal length according to the distance of object then eye become unable to see the object clearly placed at any point .This types defect in eye is known as defect of vision .
Types of defect of vision:- It is 2 types :
i)Long sightedness or hypermetropia .-The sightedness in which eye can see far object clearly but can not see the near object clearly is called long sightedness .
Causes of long sightedness :-
i)The lens become to thin .
ii)The lens has long focal length .
iii)The image of near object is formed beyond retina .
Remedy or correction of long sightedness :-
Long sightedness is corrected by using spectacles containing convex lens because it converge the ray of light and help to form image of near object on the retina .
2.)Short sightedness or myopia :-
The sightedness in which eye can see near object clearly but for object can not see clearly is known as short sightedness .
Causes of short sightedness :-
i)The lens become to thick .
ii)The lens has short focal length .
iii)The image of far object is formed at the front of retina .
Remedy or correction of short sightedness :-
The short sightedness is corrected by using spectacles containing concave lens because it diverge the ray of light and help to form image of far object on the retina.
Accommodation :-The ability of an eye to focus the distant object and far object on the retina is known as accommodation.
1.)Ramita is wearing a spectacles of power -0.5 D .What is her defect of vision .What is focal length and what types of lens is she wearing ?
Ans. Power of lens is negative ,so lens is concave lens ,If he is concave lens so she must have short sightedness defect of vision .
Given,
Power of lens(p)=-0.5D
Focal length(f) =?
By formula
P =1 /f (meter )
Or 0.5 =
Or 0.5f = 1
Or f =
Therefore ,focal length of lens(f)=2m or 200cm
Unit :- 6 Current electricity and magnetism
Electric current or electricity :-The rate of flow charge or electrons per unit time through electric circuit is called electric current .Its S.I. unit is ampere(A) and measured by ammeter(ie large amount) or Galvanometer(ie. little amount) .
Electric current (I) =Charge (Q) / Time(t)
Note :-1 coulomb charge= 6.24 ×1018 electrons
1 Ampere current :- If one coulomb charge or 6.24×1018 electrons flow in one second through a electric circuit is called 1 ampere current .
Electric circuit :-A conducting path made by connecting electric source ,load ,switch with good conducting wire is called electric current .
i)Closed circuit :- The circuit in which the load is functioning due continue flow of current through the circuit is called closed circuit .
ii)Open circuit .- The circuit in which load does not function due to switch ,broken of wire, and fuse is gone off is called open circuit .
Ammeter :- An electrical device which is used to measure the electric current flowing through the electrical circuit is called ammeter .It is always connected series with load in circuit and denoted by A.
Voltmeter An electrical device which is used to measure e. m. f. or potential difference is called voltmeter . It is connected parallel with load in circuit and denoted by V.
Potential difference (P.d.) :- The amount of work done against electrical circuit ,when one coulomb charge is carried from one point to another point of closed circuit is called potential difference between two point .It is always less than that of e.m.f because affected by resistance .It is measured by voltmeter .
Electro-motive force (E.m.f.) :- The energy supplied by electric source (Cell) ,when one coulomb charge is carried from –tive terinal to +tive terminal of electric source (cell) is called E.m.f It is always greater than that of p.d. because not affected by resistance .It is measured by voltmeter . Resistance :-The property of conductor due to which oppose the flow of current through it ,is called resistance .It is denoted by R. The relation between potential difference ,current and resistance is shown by following formula .
V = R I Where ,V= potential difference or voltage ,I = current , R = resistance .
Resistor :- The conductor that oppose the flow of current is called resistor .
Types of connection of resistor or load :-They are two types
i)Series connection of resistor or load
Total resistance (R) =R1 +R2+R3 +…….Rn
ii) Parallel connection o resistor or load :-
Total resistance ( 1/R) =1/R1 +1/R2 +1/ R3 +……..1/Rn
Domestic circuit :-An A.C. circuit which is connected in house, factories ,industries is called domestic circuit .
Wires of house hold wiring :- it is 3 types.
.
i)Phase or live wire:-The wire which possess high potential is called live or phase wire .In house hold wiring red or brown wire are used for phase .It give electric shocks.
ii)Neutral wire :-The wire which possess zero potential is called Neutral wire .In house hold wiring black or blues wire are used for neutral wire. It does not give electric shocks.
iii) Earthing wire :-The Process of connecting the metallic body of an electric appliances to earth by conducting wire is called earthing wire.in house hold wiring green or green with yellow stripes are used for earthing wire .
Functions :-It save the electric appliances from being damage in case of short circuit and overloading .
Points that we should remember during house hold wiring :-
i)switch should be connected with the live wire because, it cut the supply the of electric current to electric appliances and prevent from the chance of electric shock when switch is turn off .
ii)Fuse should be connected with live wire because, it cut the supply of electric current to the electric appliances and prevent from the chances of electric shocks when fuse gone off .
iii)Separate fuse should be used for separate flat and for an expensive or high powered appliances to prevent .
iv)Appliances must be connected in parallel for run in full efficiency .
Short circuit :-The direct connection of live wire and neutral wire in A.C. or +terminal and –terminal in D.C. is called short circuit .It causes heating the circuit and may result immediate fire due low resistance and flow of large amount current through the circuit .
Fuse :- A safety thin wire device made up an alloy of tin (63%) and lead (37%) having low melting point is called fuse .It is measured in ampere by using following formula .
Fuse (I) =P(power) /V (voltage )
The rating of fuse always selected slightly more than the current flowing in the circuit .
Functions of the fuse :-
i)It control the maximum limit of current passing through the circuit by melting itself .
ii)It prevent from the chances of electric shocks and broken of electric circuit due to overloading and short circuit by melting itself .
1)In a house a heater of 1500w ,a refrigerator of 100w,a television of 80w,3 bulb of 60w each and an iron of 1000w are used .Calculate the rating of fuse in supply of 220v A.C. to run all appliances safely .
Ans. Given,
Total power of all appliances (P)=p1+p2+p3+ p4+p5
P=1500+100+80+60×3+1000
P = 3760 watt
Voltage(V) =220v
Current (I) =?
According to formula
I =P/V
Or I = 3760 /220 = 13
Therefore ,the current is flowing in the circuit (I) =13 ampere
So the rating of fuse should be (I) = 14 A
Alternating current (A.C.) The current that change its polarity and magnitude at certain interval time is called alternating current .It can be generated from a.c. generator or dynamo. The voltage of a.c. can be increase of decrease by using transformer .
Direct current(D.C.) :- The current that does not change its polarity and magnitude at certain interval time is called direct current .It can be generated by cell or battery .The voltage of d.c. current can not be increase or decrease by using transformer but by changing number of cell.
Use of M.C.B.is better than fuse :
i)M.C.B. will automatically switch off the main supply ,if the current drawn exceeds the prescribed upper safe limit .but fuse wire melt and produces the break in the circuit .
ii)It can reset with the help of a flip over switch ,but it is difficulty to change the fuse .
Frequency of A.C. :- The number of times of change in polarity of a.c.per second is called frequency .For example: The frequency of electricity distributed in Kathmandu is 50hz.It means that the polarity of electric current distributed in Kathmandu changes 50 times per second .
Effect of current electricity :- :- The conversion of electrical energy into different form of energy is called effect of current electricity .There are different effect of current electricity :
i)Heating effect of electricity ii) Lighting effect of electricity
iii)Magnetic effect of electricity iv)Chemical effect of electricity.
1)Heating effect of electricity :-The conversion of electrical energy into heat energy by passing electricity through a wire of high resistance is called heating effect of electricity .For example: Electric heater , electric kettles etc. change electrical energy into heat energy.
Nichrome wire :-It is an alloy Nickel and chromium. It is used as heating element due to following reason or features:.
i)It has resistivity and high melting point so it can convert electrical energy heat energy .
ii)It does not react with oxygen ,even at very high temperature .
Tungsten wire :- it is an element and its symbol is W .It is used as heating element due to following reason or features: .
i)It has high resistivity and high melting point so It can convert electrical energy into light energy because it becomes white hot and emits light energy .
ii)It react with oxygen with air at very high temperature so it is always kept inside glass .
2.)Lighting effect of electricity:- The conversion of electrical energy into light energy by passing electricity through a thin wire of high resistance is called lighting effect of electricity for example :Electric bulb, electric lamp etc. change the electrical energy into light energy .
i)Filament lamp :-
The electrical lamp in which filament is which filament is used to get lighting effect of electricity is called filament lamp. Filament is a small coil of tungsten wire having very high resistivity and high melting point. Filament lamp is filled with nitrogen or argon gas to prevent the filament from evaporation ,when it is heated at high temperature .It convert only 10% of electrical energy into light energy and 90% into heat energy and efficiency is 10% .Its life span is about 1000hours .It is cheap than that fluorescent lamp.
ii) Fluorescent lamp :-The electrical lamp in which fluorescent power ( ie. Cadmium silicate ) is used to convert ultra violet rays into visible rays (to convert the light rays having short wave length into the light rays having long wave length ) is called fluorescent lamp. It is filled with mercury vapour to produce ultra violet rays when electrons from cathode strike to the mercury atoms .It convert 30% electrical energy into light energy and 70% into heat energy and efficiency is 30 % ..Its life span is about 3000 hours .It is expensive than that of filament lamp.
3.)Magnetic effect of electricity :-The conversion of electrical energy into magnetic energy by passing current through a solenoid with core of soft magnetic substance is known as magnetic effect of electricity .For example : electromagnet change electrical energy into magnetic energy.
Methods for increasing the magnetic power of electromagnet :-
i)By increasing the number of turns of wire in the coil .
ii)By increasing the strength of electric power .
iii)By using soft magnetic substances ie . iron inside solenoid .
Widely uses of electromagnet :- Due to following reasons electromagnet are widely used :
i)It is a temporary magnet so magnetic properties can be increased or decreased according to our necessity or desire .
ii)The shape of the magnet can be changed according to our desire .
iii)The strength of the magnet can be changed according to needs .
Uses of electro-magnet :-
i)It is used in the construction of electric bell ,loud speaker ,electric motor ,electric fan etc.
ii)It is used to lift and transport heavy loads ie. Big machine .
iii)It is used to separate magnetic substances from non magnetic substances
iv)It is used for removing steel splinters from the eye .
Solenoid :-A long coiled of wire with soft magnetic substances is called solenoid .
Some electro-magnetic devices and their uses :-
1.)Electric -bell :- An electrical devices which is used in houses ,school ,industries as a bell is called electrical bell.
Working :- When switch is on ,the I shaped soft iron acts as electro-magnet, so springy plate gets attracted toward the electromagnet .At same time hammer hits the gang and sound is produced but now circuit open and I shaped electro magnet become an iron by losing magnet properties so springy plate again connect with circuit .This process repeats continuously as the is on .
Uses .- i) it is used in houses ,school, office ,hospital, industries etc. for information.
Motor effect :- When current carrying conductor is kept in a magnetic field ,a movement is developed in the conductor continuously .This called motor effect .It takes place due to attraction and repulsion between external magnetic field and that of current around the wire. For example : electric motor ,electric fan based on the principle of motor effect .
2.)Electric motor :-An electrical device that electrical energy into kinetic energy is called electric motor .
Principle :-It based on the principle of motor effect. permanent magnet is used in electric motor .
Types of motor :- They are two types :
i)AC motor that is uses AC supply.ie. motor of fan ,motor of washing machine .
ii)DC motor that uses DC Supply. ie. the motor of battery operated appliances .
Construction and working .- It consist of coils between two poles of strong magnet .When the current is passed through the coils a magnetic field is set up around it .This magnetic field interacts with the magnetic field interacts with the magnetic field of the magnet .As a result ,the coil experiences a force due to which it begin to rotates.
Uses :- i)It is used to run industries ,factories etc.
ii)It is used to run different electrical appliances .
Magnetic lines of force :-The imaginary curve drawn N-Pole to S-pole around magnet that show the direction of magnetic force is called magnetic lines of force .
Properties of magnetic lines of force :- i)They are continuous closed curves.
ii)The magnetic lines of force moves from N-Pole to S-pole .
iii)The magnetic lines of force does not intersect each other.
Magnetic flux :-Total n. of magnetic lines of force present in an area is called magnetic flux.
Electro-magnetic induction :-The process by which electric current is induced in a closed circuit due to change in magnetic flux through a closed circuit is called electro-magnetic induction .for example: Dynamo or generator based on principle of electro-magnetic induction.
Induced current :- The current produced in a conductor by electro-magnetic induction is called induced current .
Induced e.m.f. :-The electro- motive force (voltage) produced by electro-magnetic induction is called electro-motive force .
Faraday’s electro-magnetic induction :-
i)When there is change in magnetic flux linked with closed a circuit emf is induced in the circuit .
ii)The magnitude of induced emf is directly proportional to rate of change magnetic flux .
iii)The induced emf last as long as the change in the magnetic flux.
3.)Dynamo :- An electrical device which produce electric current by the process of electric magnetic induction is called dynamo. It produce small amount of electricity .it convert kinetic energy into electrical energy .
Principle :- It is based on principle of electro-magnetic induction .
Working :- It consist of rotating head with a magnet Below the magnet an isolated copper wire around the soft iron is kept .This all system is sealed with an aluminum pot .when head is rotated with help of wheel magnet also moves, due to which magnetic flux change and emf is induced in coil , that flow through the wire .
Uses :-i)It is used to produce small amount of current electricity for operating electrical device .
Generator :-An electrical device which produce large a amount of current electricity by process of electro- magnetic induction is called generator .It convert kinetic energy into electrical energy .
Principle :- it based on the principle of electro –magnetic induction .
Working :- It consist of rectangular coil of a wire ,which is rotated between two opposite poles of strong magnet .when rectangular coli is rotated with help of turbine due to which magnetic flux change and emf is induced in the coil .that flow through the wire .
Uses - It is used to produce large amount of electricity for operating industries ,factories etc. .
Methods to increase strength of dynamo or generator:-
i)By increasing the number of turns of coil .
ii) By increasing strength of the magnet .
iii) By increasing the speed of rotation of magnetic field , or by increasing the speed of rotation of coil in the magnetic field .
iv)By decreasing the distance between magnet and the coil.
Electric appliances and their uses :-
1.)Inverter :- An electrical device that convert alternating current into direct current and direct current into alternating is known as inverter .
Working: When alternating current flow in the circuit then it is converted into direct current by inverter and stored into a battery .But ,if main line is off then inverter convert direct current into alternating current and electric appliances works .
2.)Charger :- An electrical device that convert alternating current into direct current and stored in a battery is called charger .when battery is full charge then the cut off system inside battery by charger.
Uses i) It Is used to charge the battery of mobile ,laptop ,radio ,Camera etc .
3.)Transformer:- An electrical device which convert high alternating voltage into low alternating voltage and low alternating voltage into high alternating voltage is called transformer .
Principle of transformer :-It is based on principle of of mutual induction ie. when an alternating current is passed into one coil an induced current is produced in the neighboring or adjacent coil.
Construction and working ;- It consist of three major parts ie. soft iron core, primary coil ,and secondary coil .
soft iron core consist of rectangular frame of thin laminated sheets of soft iron .Each sheet is laminated by varnish or shellac in order to prevent from loss of current by reducing heating effect and soft iron has very high magnetic permeability so it help to concentrate magnetic line of force.
The coil in which alternating current is supplied is called primary coil and the voltage supplied in primary coil is called primary voltage .
The coil in which electric current is induced is called secondary coil and the voltage of secondary coil is called secondary voltage .
The current supplied in the transformer is called input current and the current produced from the transformer is called output current .
In transformer number of turns of primary coil should be about 1000 for greater efficiency and durability and prevent from heat, loss of energy ,and of short circuit .
Relation between primary coil(n1),secondary coil(n2),primary voltage(v1) and secondary voltage(v2).:
Or v2 / v1 = n2 / n1 
Type of transformer :- They are two types :
1.)Step up transformer :-A transformer which convert low alternating voltage into high alternating voltage is called step up transformer. In step up transformer number of turns secondary coil is always more than that of number of turns of primary coil it is also used to transmit electricity for long distance . .For example: it is used in power station ,tv, computer x-ray tube, etc
Advantages of transformer :-
i)It help to convert high alternating voltage into low alternating voltage and low alternating voltage into high alternating voltage .
ii)It is used for long distance transmission of alternating current through aluminum wire .
Uses :-
I)Step up transformer is used for long transmission of ac through aluminum wire .
ii) Step up transformer is used in power station ,computer,tv.x-ray tube. etc.
ii)Step down transformer is used in radio ,electric bell, battery charger etc.
Safely measures of for using electricity :-They are as follows:
i)High quality ,and suitable amperage and insulated wire should be used .
ii)Naked wire or taped wire should be covered by insulated tape.
iii)Suitable capacity of fuse should be used .
iv) Earthing should be done .
v)Fuse and switch should be connected to live wire .
Electric power :- The rate of conversion of electrical energy into other forms of energies by different devices in a circuit is called electric power .Its S.I. unit is watt .
Electric power (P) =current (I) ×voltage(v)
Prove that P = I×V
We know that,
Power (P) =work done (w) /time taken
P = W / t (i)
Again,
Potential difference (V.) = Work done (W) / Charge (Q)
Or w = V×Q ( ii)
From eqn (i) and (ii)
P = V x Q / t
Or P = V×Q /t (because I =Q /t )
؞ P = I× V Proved
Electrical power consumption :- The energy power conversion by different electric load into other forms of energy in domestic circuit are called electrical power consumption .Its S.I. unit is kilo watt hour(kwh) or unit .
Electrical energy consumption(E) =power of device (in kw) ×Number of device ×time of use(In hr)
Or E = P(inkw) × N × t(inhr)
Cost of electricity(C) =Total consumed unit × price of one unit
One unit :-Power consumed by electric load of power 1kw in one hour is called one unit power consumption.
1 unit = 1 kw ×I hour
1unit = 1kwh
Rating of electrical device :- The maximum value of current (I),potential difference (v) and power (P) that can be supplied to a particular electrical device for its operation is called rating of electrical device .
Some electrical appliances and their power consumed at 220v.
i)Tube light = 40 watt
ii)Fan = 60watt
iii)Refrigerator = 100 watt
iv)Television = 100 watt
v)Electric kettle= 750 watt
vi)Electric iron = 1000 watt
vii)Air conditioner = 2000 watt- 3000 watt
viii)Electric mixture =750 watt
ix)Immersion rod = 1000 watt
1.)What is meant by the rating of an electric bulb is 60 watt(j/s)?
Ans. It means that electrical bulb convert 60 j of electrical energy into heat energy and light energy per second .
Numerical problems
Formula :
i)P = I×V
ii) V =R×I
iii)Energy consumption (E)= P(in kw)×N×t(in hr)
iv) V2 / V1= n2 / n1
v) I1V2 = I2V1
i)An electrical heater draws a current of 10 A from a 220 volt supply .What is the cost of using the heater for 5 hours for 30 days .If 1nit of electricity costs Rs 9 ?
Given,
Voltage(v)=220 v
Current (I) =10 A
Time consumption per day (t)= hours
Rate of electricity(R) =Rs 9 per unit
By formula
Electrical power(P)=I×V
Or P =10 ×220
Or p = 2200watt
Now, Per day electrical power consumption(E)=P(kw) × N × t(hr)
Or E= 2200×1×5
Or E =11000whr =11000 /1000 =11kwhr or unit
؞One month electrical power consumption (E)=11×30
Or E =330 kwhr or unit
Again, by formul×a
One month cost of electricity(C) = Total consumed unit × price of one unit
=330×9
Total cost of 30 days(C) =Rs2970.
2.)A circuit with 220 v is supplied with fuse of 5A. How many bulbs of 100 watt can be safely used in the circuit .
Given,
Current (I)=5 A
Voltage(v)=220 v
By formula
Total power (P) =I×V
Or P =5×220
Total power (P)1100 watt
Power of bulb (P’) =100watt
For the safety of the circuit
P =P’×n
؞Number of bulb safely used (n) = P /P’
Or n =1100 /100 = 1
3.)In a house 12 tube light of 40 watt for 4 hours, 3 tv of 440 watt used for 4 hours ,electric immersion rods of 750 watt used 2hours and 2 electric bulb of 100 watt is used for 2 hours daily. Find the the cost of electricity in a month if the cost of electricity per unit is Rs7.00.
Given,
By formula
Per day electrical consumption
i)for 12 tube ligt(E1) =P(kw) × N × t(hr)
E1 = 40×12×4
E1= 1920 whr. =1920 /1000 =19.2kwhr or unit.
ii)For television(E2)=p(kw) ×N×t(hr)
E2 =40×3×4
E2=480 whr =480 /1000 = 0.48 kwhr or unit
iii)For electrical immersion rod(E3) =P(whr) × N × t(hr)
E3 =750×2×2
E3 =3000 whr =3000 /1000 =3kwhr or unit
iv)For electric bulb(E4) =P(kw) ×N× t (hr)
E4 = 100 ×2×2
E4 = 400 whr =400 /1000 =0.4 kwhr or unit
Total electrical consumption of on day (E)=E1+E2+E3+E4
=19.2+0.48+3+0.4
=5.08 kwhr or unit
Total electrical power consumption of 30 days (E)=5.08 ×30
=174 kwhr or unit
By formula
Cost of one month ( C) =Total consumed unit× Cost of 1 unit
=174 ×7 =Rs 1218.
4.)A transformer is of 220 v primary voltage has 770 turns of secondary coil will be necessary in order to produce 120 volt from that transformer ?
Ans.Given,
Primary voltage(v1) = 220 v
Primary turns (n1)= 770
Secondary voltage (v2)= 120 v
Secondary coil(n2) =?
By formula
V2 / V1= n2 / n1
Or 120 /220 = n2 /770
n2 =120 x 770 / 220
؞Secondary coil (n2) = 420
6.)A transformer has 240 input voltage .30A input current and 120 v out put voltage ,than calculate out put current ..
Ans. Given ,
Primary voltage(v1)= 220 v
Input current (I1)= 30A
Secondary voltage(V2)=120 v
Out put current (I2)= ?
By formula
I1V1 = I2V2
Or 30×240 =I2×120
Or I2 =30 x 240 /120
؞Out put current (I2)=60A
7.)The number of turns in primary winding of certain transformer is 150 times more than that in the secondary winding .Calculate the input emf in the primary winding, if the emf generated in the secondary winding is 220 v.
Ans. Given,
Number of secondary winding (n2)=X
Number of primary winding (n1)=150X
Secondary voltage (V2)=220
Primary voltage (V1) =?
By formula
V2 / V1= n2 / n1 
Or 220 /v1 =x /150x
Or V1 = 220×150
؞Primary voltage (V1) = 33000 volt
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