JEE Main 2020 Physics September 4 Shift 2 Paper & Solutions | Mock Tests for JEE Main and Advanced 2025 PDF Download

 Page 1


JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 1
Date : 4th September 2020
Time : 02 : 00 pm - 05 : 00 pm
Subject : Physics
 1. A circular coil has moment of inertia 0.8 kg m
2
 around any diameter and is carrying
current to produce a magnetic moment of 20 Am
2
. The coil is kept initially in a vertical
position and it can rotate freely around a horizontal diameter. When a uniform magnetic
field of 4 T is applied along the vertical,it starts rotating around its horizontal diameter.
The angular speed the coil acquires after rotating by 60° will be:
(1) 10 ? rad s
–1
(2) 20 rad s
–1
(3) 20 ? rad s
–1
(4) 10 rad s
–1
Sol. 4
By energy conservation
i i f f
U K U K ? ? ?
2
1
MBcos60 0 MBcos 0 I
2
? ? ? ? ? ? ? ?
2
MB 1
MB I
2 2
? ? ? ?
2
MB 1
I
2 2
? ?
MB 20 4
100
I 0.8
?
? ? ? ? = 10 rad/s
2. A person pushes a box on a rough horizontal platform surface. He applies a force of 200
N over a distance of 15 m. Thereafter, he gets progressively tired and his applied force
reduces linearly with distance to 100 N. The total distance through which the box has
been moved is 30 m. What is the work done by the person during the total movement
of the box?
(1) 5690 J (2) 5250 J (3) 2780 J (4) 3280 J
Sol. 2
A
B
C
30 15
O
D
100
Force 
disp (in m) (in N)
200
E
Work done = area of ABCEO
= area of trap. ABCD + area of rect. ODCE
= 
1
45 100 100 30 5250J
2
? ? ? ? ?
Page 2


JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 1
Date : 4th September 2020
Time : 02 : 00 pm - 05 : 00 pm
Subject : Physics
 1. A circular coil has moment of inertia 0.8 kg m
2
 around any diameter and is carrying
current to produce a magnetic moment of 20 Am
2
. The coil is kept initially in a vertical
position and it can rotate freely around a horizontal diameter. When a uniform magnetic
field of 4 T is applied along the vertical,it starts rotating around its horizontal diameter.
The angular speed the coil acquires after rotating by 60° will be:
(1) 10 ? rad s
–1
(2) 20 rad s
–1
(3) 20 ? rad s
–1
(4) 10 rad s
–1
Sol. 4
By energy conservation
i i f f
U K U K ? ? ?
2
1
MBcos60 0 MBcos 0 I
2
? ? ? ? ? ? ? ?
2
MB 1
MB I
2 2
? ? ? ?
2
MB 1
I
2 2
? ?
MB 20 4
100
I 0.8
?
? ? ? ? = 10 rad/s
2. A person pushes a box on a rough horizontal platform surface. He applies a force of 200
N over a distance of 15 m. Thereafter, he gets progressively tired and his applied force
reduces linearly with distance to 100 N. The total distance through which the box has
been moved is 30 m. What is the work done by the person during the total movement
of the box?
(1) 5690 J (2) 5250 J (3) 2780 J (4) 3280 J
Sol. 2
A
B
C
30 15
O
D
100
Force 
disp (in m) (in N)
200
E
Work done = area of ABCEO
= area of trap. ABCD + area of rect. ODCE
= 
1
45 100 100 30 5250J
2
? ? ? ? ?
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 2
3. Match the thermodynamic processes taking place in a system with the correct conditions.
In the table : ?Q is the heat supplied, ?W is the work done and ?U is change in internal
energy of the system.
     Process Condition
(I) Adiabatic (1) ?W = 0
(II) Isothermal (2) ?Q = 0
(III) Isochoric (3) ?U ? ?0, ?W ? 0,
      ?Q ? 0
(IV) Isobaric (4) ?U = 0
(1) (I) - (1), (II) - (1), (III) - (2), (IV) - (3)
(2) (I) - (1), (II) - (2), (III) - (4), (IV) - (4)
(3) (I) - (2), (II) - (4), (III) - (1), (IV) - (3)
(4) (I) - (2), (II) - (1), (III) - (4), (IV) - (3)
Sol. 3
adiabatic, ?Q = 0
Isothermal, ?U = 0
Isochoric, pdV 0 ?
?
W 0 ? ?
Isobaric, Q 0, U 0, W 0 ? ? ? ? ? ?
4. The driver of a bus approaching a big wall notices that the frequency of his bus’s horn
changes from 420 Hz to 490 Hz when he hears it after it gets reflected from the wall.
Find the speed of the bus if speed of the sound is 330 ms
–1
.
(1) 81 kmh
–1
(2) 91 kmh
–1
(3) 71 kmh
–1
(4) 61 kmh
–1
Sol. 2
Freq received by wall,
w 0
330
f f
330 v
? ?
?
? ?
? ? ?
freq. after reflection, w
330 v
f ' f
330
? ? ?
?
? ?
? ?
= 0
330 v 330
f
330 330 v
? ? ? ? ?
?
? ? ? ?
? ? ? ? ?
330 v
490 420
330 v
? ? ?
?
? ?
? ? ?
v 25.2 m/s ? ?
= 91 km/h
5. A small ball of mass m is thrown upward with velocity u from the ground. The ball
experiences a resistive force mkv
2
 where v is its speed. The maximum height attained by
the ball is:
(1)
–1
1 ku
tan
k 2g
?
(2) 
1 ku
ln 1
2k g
?
? ?
?
? ?
? ?
(3) 
1 ku
ln 1
k 2g
?
? ?
?
? ?
? ?
(4) 
2
1
1 ku
tan
2k g
?
Page 3


JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 1
Date : 4th September 2020
Time : 02 : 00 pm - 05 : 00 pm
Subject : Physics
 1. A circular coil has moment of inertia 0.8 kg m
2
 around any diameter and is carrying
current to produce a magnetic moment of 20 Am
2
. The coil is kept initially in a vertical
position and it can rotate freely around a horizontal diameter. When a uniform magnetic
field of 4 T is applied along the vertical,it starts rotating around its horizontal diameter.
The angular speed the coil acquires after rotating by 60° will be:
(1) 10 ? rad s
–1
(2) 20 rad s
–1
(3) 20 ? rad s
–1
(4) 10 rad s
–1
Sol. 4
By energy conservation
i i f f
U K U K ? ? ?
2
1
MBcos60 0 MBcos 0 I
2
? ? ? ? ? ? ? ?
2
MB 1
MB I
2 2
? ? ? ?
2
MB 1
I
2 2
? ?
MB 20 4
100
I 0.8
?
? ? ? ? = 10 rad/s
2. A person pushes a box on a rough horizontal platform surface. He applies a force of 200
N over a distance of 15 m. Thereafter, he gets progressively tired and his applied force
reduces linearly with distance to 100 N. The total distance through which the box has
been moved is 30 m. What is the work done by the person during the total movement
of the box?
(1) 5690 J (2) 5250 J (3) 2780 J (4) 3280 J
Sol. 2
A
B
C
30 15
O
D
100
Force 
disp (in m) (in N)
200
E
Work done = area of ABCEO
= area of trap. ABCD + area of rect. ODCE
= 
1
45 100 100 30 5250J
2
? ? ? ? ?
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 2
3. Match the thermodynamic processes taking place in a system with the correct conditions.
In the table : ?Q is the heat supplied, ?W is the work done and ?U is change in internal
energy of the system.
     Process Condition
(I) Adiabatic (1) ?W = 0
(II) Isothermal (2) ?Q = 0
(III) Isochoric (3) ?U ? ?0, ?W ? 0,
      ?Q ? 0
(IV) Isobaric (4) ?U = 0
(1) (I) - (1), (II) - (1), (III) - (2), (IV) - (3)
(2) (I) - (1), (II) - (2), (III) - (4), (IV) - (4)
(3) (I) - (2), (II) - (4), (III) - (1), (IV) - (3)
(4) (I) - (2), (II) - (1), (III) - (4), (IV) - (3)
Sol. 3
adiabatic, ?Q = 0
Isothermal, ?U = 0
Isochoric, pdV 0 ?
?
W 0 ? ?
Isobaric, Q 0, U 0, W 0 ? ? ? ? ? ?
4. The driver of a bus approaching a big wall notices that the frequency of his bus’s horn
changes from 420 Hz to 490 Hz when he hears it after it gets reflected from the wall.
Find the speed of the bus if speed of the sound is 330 ms
–1
.
(1) 81 kmh
–1
(2) 91 kmh
–1
(3) 71 kmh
–1
(4) 61 kmh
–1
Sol. 2
Freq received by wall,
w 0
330
f f
330 v
? ?
?
? ?
? ? ?
freq. after reflection, w
330 v
f ' f
330
? ? ?
?
? ?
? ?
= 0
330 v 330
f
330 330 v
? ? ? ? ?
?
? ? ? ?
? ? ? ? ?
330 v
490 420
330 v
? ? ?
?
? ?
? ? ?
v 25.2 m/s ? ?
= 91 km/h
5. A small ball of mass m is thrown upward with velocity u from the ground. The ball
experiences a resistive force mkv
2
 where v is its speed. The maximum height attained by
the ball is:
(1)
–1
1 ku
tan
k 2g
?
(2) 
1 ku
ln 1
2k g
?
? ?
?
? ?
? ?
(3) 
1 ku
ln 1
k 2g
?
? ?
?
? ?
? ?
(4) 
2
1
1 ku
tan
2k g
?
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 3
Sol. 2
v
mg mkv
2
 at H
m
 , V = 0
F
net
 = ma
2
dv
mg mKv mv
ds
? ? ?
? ?
H v 0
2
S 0 v u
vdv
ds 1
g kv
?
? ?
? ?
?
? ?
       
2
xdx
a bx ?
?
2
max
1 g ku
H n
2k g
? ? ?
?
? ?
? ?
?
2
m
1 ku
H n 1
2k g
? ?
? ?
? ?
? ?
?
6. Consider two uniform discs of the same thickness and different radii R
1
 = R and R
2
 = ?R
made of the same material. If the ratio of their moments of inertia I
1
 and I
2
, respectively,
about their axes is I
1
 : I
2
 = 1 : 16 then the value of ? is :
(1) 
2
(2) 2 (3) 
2 2
(4) 4
Sol. 2
Moment of inertia of disc, 
? ?
2 2
2
R t R
MR
I
2 2
? ?
? ?
? ?
? ?
I = KR
4
4
1 1
2 2
I R
I R
? ?
?
? ?
? ?
? ?
4
1
4
1 R
16 2
16 R
? ?
? ? ? ? ?
? ?
? ? ?
Page 4


JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 1
Date : 4th September 2020
Time : 02 : 00 pm - 05 : 00 pm
Subject : Physics
 1. A circular coil has moment of inertia 0.8 kg m
2
 around any diameter and is carrying
current to produce a magnetic moment of 20 Am
2
. The coil is kept initially in a vertical
position and it can rotate freely around a horizontal diameter. When a uniform magnetic
field of 4 T is applied along the vertical,it starts rotating around its horizontal diameter.
The angular speed the coil acquires after rotating by 60° will be:
(1) 10 ? rad s
–1
(2) 20 rad s
–1
(3) 20 ? rad s
–1
(4) 10 rad s
–1
Sol. 4
By energy conservation
i i f f
U K U K ? ? ?
2
1
MBcos60 0 MBcos 0 I
2
? ? ? ? ? ? ? ?
2
MB 1
MB I
2 2
? ? ? ?
2
MB 1
I
2 2
? ?
MB 20 4
100
I 0.8
?
? ? ? ? = 10 rad/s
2. A person pushes a box on a rough horizontal platform surface. He applies a force of 200
N over a distance of 15 m. Thereafter, he gets progressively tired and his applied force
reduces linearly with distance to 100 N. The total distance through which the box has
been moved is 30 m. What is the work done by the person during the total movement
of the box?
(1) 5690 J (2) 5250 J (3) 2780 J (4) 3280 J
Sol. 2
A
B
C
30 15
O
D
100
Force 
disp (in m) (in N)
200
E
Work done = area of ABCEO
= area of trap. ABCD + area of rect. ODCE
= 
1
45 100 100 30 5250J
2
? ? ? ? ?
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 2
3. Match the thermodynamic processes taking place in a system with the correct conditions.
In the table : ?Q is the heat supplied, ?W is the work done and ?U is change in internal
energy of the system.
     Process Condition
(I) Adiabatic (1) ?W = 0
(II) Isothermal (2) ?Q = 0
(III) Isochoric (3) ?U ? ?0, ?W ? 0,
      ?Q ? 0
(IV) Isobaric (4) ?U = 0
(1) (I) - (1), (II) - (1), (III) - (2), (IV) - (3)
(2) (I) - (1), (II) - (2), (III) - (4), (IV) - (4)
(3) (I) - (2), (II) - (4), (III) - (1), (IV) - (3)
(4) (I) - (2), (II) - (1), (III) - (4), (IV) - (3)
Sol. 3
adiabatic, ?Q = 0
Isothermal, ?U = 0
Isochoric, pdV 0 ?
?
W 0 ? ?
Isobaric, Q 0, U 0, W 0 ? ? ? ? ? ?
4. The driver of a bus approaching a big wall notices that the frequency of his bus’s horn
changes from 420 Hz to 490 Hz when he hears it after it gets reflected from the wall.
Find the speed of the bus if speed of the sound is 330 ms
–1
.
(1) 81 kmh
–1
(2) 91 kmh
–1
(3) 71 kmh
–1
(4) 61 kmh
–1
Sol. 2
Freq received by wall,
w 0
330
f f
330 v
? ?
?
? ?
? ? ?
freq. after reflection, w
330 v
f ' f
330
? ? ?
?
? ?
? ?
= 0
330 v 330
f
330 330 v
? ? ? ? ?
?
? ? ? ?
? ? ? ? ?
330 v
490 420
330 v
? ? ?
?
? ?
? ? ?
v 25.2 m/s ? ?
= 91 km/h
5. A small ball of mass m is thrown upward with velocity u from the ground. The ball
experiences a resistive force mkv
2
 where v is its speed. The maximum height attained by
the ball is:
(1)
–1
1 ku
tan
k 2g
?
(2) 
1 ku
ln 1
2k g
?
? ?
?
? ?
? ?
(3) 
1 ku
ln 1
k 2g
?
? ?
?
? ?
? ?
(4) 
2
1
1 ku
tan
2k g
?
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 3
Sol. 2
v
mg mkv
2
 at H
m
 , V = 0
F
net
 = ma
2
dv
mg mKv mv
ds
? ? ?
? ?
H v 0
2
S 0 v u
vdv
ds 1
g kv
?
? ?
? ?
?
? ?
       
2
xdx
a bx ?
?
2
max
1 g ku
H n
2k g
? ? ?
?
? ?
? ?
?
2
m
1 ku
H n 1
2k g
? ?
? ?
? ?
? ?
?
6. Consider two uniform discs of the same thickness and different radii R
1
 = R and R
2
 = ?R
made of the same material. If the ratio of their moments of inertia I
1
 and I
2
, respectively,
about their axes is I
1
 : I
2
 = 1 : 16 then the value of ? is :
(1) 
2
(2) 2 (3) 
2 2
(4) 4
Sol. 2
Moment of inertia of disc, 
? ?
2 2
2
R t R
MR
I
2 2
? ?
? ?
? ?
? ?
I = KR
4
4
1 1
2 2
I R
I R
? ?
?
? ?
? ?
? ?
4
1
4
1 R
16 2
16 R
? ?
? ? ? ? ?
? ?
? ? ?
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 4
7. A series L-R circuit is connected to a battery of emf V. If the circuit is switched on at t =
0, then the time at which the energy stored in the inductor reaches 
1
n
? ?
? ?
? ?
 times of its
maximum value, is :
(1) 
L n
ln
R
n 1
? ?
? ?
? ?
?
? ?
(2) 
L n
ln
R
n –1
? ?
? ?
? ?
? ?
(3) 
L n 1
ln
R
n –1
? ?
?
? ?
? ?
? ?
(4) 
L n –1
ln
R
n
? ?
? ?
? ?
? ?
Sol. 2
L
R
V
P.E. in inductor, 
2
1
U LI
2
?
2
U I ?
2
0 0
U I
U I
? ?
?
? ?
? ?
2
0
1 I
n I
? ?
?
? ?
? ?
0
I
I
n
?
R
t
L
0
I I 1 e
? ? ?
? ?
? ?
? ?
R
t
0 L
0
I
I 1 e
n
? ? ?
? ?
? ?
? ?
taking ?n  & solving we get,
L n
t n
R n 1
? ?
?
? ?
? ?
?
? ?
?
Page 5


JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 1
Date : 4th September 2020
Time : 02 : 00 pm - 05 : 00 pm
Subject : Physics
 1. A circular coil has moment of inertia 0.8 kg m
2
 around any diameter and is carrying
current to produce a magnetic moment of 20 Am
2
. The coil is kept initially in a vertical
position and it can rotate freely around a horizontal diameter. When a uniform magnetic
field of 4 T is applied along the vertical,it starts rotating around its horizontal diameter.
The angular speed the coil acquires after rotating by 60° will be:
(1) 10 ? rad s
–1
(2) 20 rad s
–1
(3) 20 ? rad s
–1
(4) 10 rad s
–1
Sol. 4
By energy conservation
i i f f
U K U K ? ? ?
2
1
MBcos60 0 MBcos 0 I
2
? ? ? ? ? ? ? ?
2
MB 1
MB I
2 2
? ? ? ?
2
MB 1
I
2 2
? ?
MB 20 4
100
I 0.8
?
? ? ? ? = 10 rad/s
2. A person pushes a box on a rough horizontal platform surface. He applies a force of 200
N over a distance of 15 m. Thereafter, he gets progressively tired and his applied force
reduces linearly with distance to 100 N. The total distance through which the box has
been moved is 30 m. What is the work done by the person during the total movement
of the box?
(1) 5690 J (2) 5250 J (3) 2780 J (4) 3280 J
Sol. 2
A
B
C
30 15
O
D
100
Force 
disp (in m) (in N)
200
E
Work done = area of ABCEO
= area of trap. ABCD + area of rect. ODCE
= 
1
45 100 100 30 5250J
2
? ? ? ? ?
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 2
3. Match the thermodynamic processes taking place in a system with the correct conditions.
In the table : ?Q is the heat supplied, ?W is the work done and ?U is change in internal
energy of the system.
     Process Condition
(I) Adiabatic (1) ?W = 0
(II) Isothermal (2) ?Q = 0
(III) Isochoric (3) ?U ? ?0, ?W ? 0,
      ?Q ? 0
(IV) Isobaric (4) ?U = 0
(1) (I) - (1), (II) - (1), (III) - (2), (IV) - (3)
(2) (I) - (1), (II) - (2), (III) - (4), (IV) - (4)
(3) (I) - (2), (II) - (4), (III) - (1), (IV) - (3)
(4) (I) - (2), (II) - (1), (III) - (4), (IV) - (3)
Sol. 3
adiabatic, ?Q = 0
Isothermal, ?U = 0
Isochoric, pdV 0 ?
?
W 0 ? ?
Isobaric, Q 0, U 0, W 0 ? ? ? ? ? ?
4. The driver of a bus approaching a big wall notices that the frequency of his bus’s horn
changes from 420 Hz to 490 Hz when he hears it after it gets reflected from the wall.
Find the speed of the bus if speed of the sound is 330 ms
–1
.
(1) 81 kmh
–1
(2) 91 kmh
–1
(3) 71 kmh
–1
(4) 61 kmh
–1
Sol. 2
Freq received by wall,
w 0
330
f f
330 v
? ?
?
? ?
? ? ?
freq. after reflection, w
330 v
f ' f
330
? ? ?
?
? ?
? ?
= 0
330 v 330
f
330 330 v
? ? ? ? ?
?
? ? ? ?
? ? ? ? ?
330 v
490 420
330 v
? ? ?
?
? ?
? ? ?
v 25.2 m/s ? ?
= 91 km/h
5. A small ball of mass m is thrown upward with velocity u from the ground. The ball
experiences a resistive force mkv
2
 where v is its speed. The maximum height attained by
the ball is:
(1)
–1
1 ku
tan
k 2g
?
(2) 
1 ku
ln 1
2k g
?
? ?
?
? ?
? ?
(3) 
1 ku
ln 1
k 2g
?
? ?
?
? ?
? ?
(4) 
2
1
1 ku
tan
2k g
?
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 3
Sol. 2
v
mg mkv
2
 at H
m
 , V = 0
F
net
 = ma
2
dv
mg mKv mv
ds
? ? ?
? ?
H v 0
2
S 0 v u
vdv
ds 1
g kv
?
? ?
? ?
?
? ?
       
2
xdx
a bx ?
?
2
max
1 g ku
H n
2k g
? ? ?
?
? ?
? ?
?
2
m
1 ku
H n 1
2k g
? ?
? ?
? ?
? ?
?
6. Consider two uniform discs of the same thickness and different radii R
1
 = R and R
2
 = ?R
made of the same material. If the ratio of their moments of inertia I
1
 and I
2
, respectively,
about their axes is I
1
 : I
2
 = 1 : 16 then the value of ? is :
(1) 
2
(2) 2 (3) 
2 2
(4) 4
Sol. 2
Moment of inertia of disc, 
? ?
2 2
2
R t R
MR
I
2 2
? ?
? ?
? ?
? ?
I = KR
4
4
1 1
2 2
I R
I R
? ?
?
? ?
? ?
? ?
4
1
4
1 R
16 2
16 R
? ?
? ? ? ? ?
? ?
? ? ?
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 4
7. A series L-R circuit is connected to a battery of emf V. If the circuit is switched on at t =
0, then the time at which the energy stored in the inductor reaches 
1
n
? ?
? ?
? ?
 times of its
maximum value, is :
(1) 
L n
ln
R
n 1
? ?
? ?
? ?
?
? ?
(2) 
L n
ln
R
n –1
? ?
? ?
? ?
? ?
(3) 
L n 1
ln
R
n –1
? ?
?
? ?
? ?
? ?
(4) 
L n –1
ln
R
n
? ?
? ?
? ?
? ?
Sol. 2
L
R
V
P.E. in inductor, 
2
1
U LI
2
?
2
U I ?
2
0 0
U I
U I
? ?
?
? ?
? ?
2
0
1 I
n I
? ?
?
? ?
? ?
0
I
I
n
?
R
t
L
0
I I 1 e
? ? ?
? ?
? ?
? ?
R
t
0 L
0
I
I 1 e
n
? ? ?
? ?
? ?
? ?
taking ?n  & solving we get,
L n
t n
R n 1
? ?
?
? ?
? ?
?
? ?
?
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-2), Physics     Page | 5
8. The electric field of a plane electromagnetic wave is given by
? ?
? ?
? ?
0
E E x y sin kz – t ? ? ?
?
Its magnetic field will be given by :
(1) 
? ?
? ?
? ?
0
E
x y sin kz – t
c
? ? (2) 
? ?
? ?
? ?
0
E
x – y sin kz – t
c
?
(3) 
? ?
? ?
? ?
0
E
x – y cos kz – t
c
? (4) 
? ?
? ?
? ?
0
E
–x y sin kz – t
c
? ?
Sol. (4)
E B ?
? ?
 should be in direction of 
v
?
? ? ? ?
0
E
ˆ ˆ B x y sin kz t
c
? ? ? ? ? ?
?
9. A cube of metal is subjected to a hydrostatic pressure of 4 GPa. The percentage change
in the length of the side of the cube is close to :
(Given bulk modulus of metal, B = 8 × 10
10
 Pa)
(1) 0.6 (2) 20 (3) 1.67 (4) 5
Sol. (3)
? ?
P
B
V
V
?
? ?
?
V
P .B
V
?
? ?
= 
3 L
B
L
?
?
L P
L 3B
? ?
? ?
% ? we get, 
L
100%
L
?
?
Putting values we get = 1.67
10. A paramagnetic sample shows a net magnetisation of 6 A/m when it is placed in an
external magnetic field of 0.4 T at a temperature of 4 K. When the sample is placed in an
external magnetic field of 0.3 T at a temperature of 24 K, then the magnetisation will
be:
(1) 4 A/m (2) 1 A/m (3) 0.75 A/m (4) 2.25 A/m
Sol. (3)
ext
CB
M
T
?
6 = 
C 0.4
4
?
? C = 60
? case - II :- M = 
60 0.3
24
?
 = 
60 3
240
?
 = 
3
4
 = 0.75 A/m