WBJEE Previous Year Question Paper - 2020 | WBJEE Sample Papers, Section Wise & Full Mock Tests 2026 PDF Download

 Page 1


Category I (Q. Nos. 1 to 30)
Carry 1 marks each and only one option is
correct. In case of incorrect answer or any
combination of more than one answer, 1/4 mark
will be deducted.
1. The intensity of light emerging from one of
the slits in a Young’s double slit experiment
is found to be 1.5 times the intensity of light
emerging from the other slit. What will be
the approximate ratio of intensity of an
interference maximum to that of an
interference minimum?
(a) 2.25 (b) 98 (c) 5 (d) 9.9
2. In a Fraunhofer diffraction experiment, a
single slit of width 0.5 mm is illuminated by
a monochromatic light of wavelength
600 nm. The diffraction pattern is observed
on a screen at a distance of 50 cm from the
slit. What will be the linear separation of the
first order minima?
(a) 1.0 mm (b) 1.1 mm
(c) 0.6 mm (d) 1.2 mm
3. If R is the Rydberg constant in cm
-1
, then
hydrogen atom does not emit any radiation
of wavelength in the range of
(a)
1
R
to
4
3R
cm (b)
7
5R
to
19
5R
cm
(c)
4
R
to
36
5R
cm (d)
9
R
to
144
7R
cm
4. A nucleus X emits a ß-particle to produce a
nucleus Y. If their atomic masses are M
x
and
M
y
respectively, then the maximum energy of
the ß-particle emitted is (where, m
e
is the
mass of an electron and c is the velocity of
light)
(a)( ) M M m c
x y e
- -
2
(b)( ) M M m c
x y e
- +
2
(c)( ) M M c
x y
-
2
(d)( ) M M m c
x y e
- -2
2
5. For nuclei with mass number close to 119
and 238, the binding energies per nucleon are
approximately 7.6 MeV and 8.6 MeV,
respectively. If a nucleus of mass number 238
breaks into two nuclei of nearly equal masses,
what will be the approximate amount of
energy released in the process of fission?
(a) 214 MeV (b) 119 MeV
(c) 2047 MeV (d) 1142 MeV
6. A common emitter transistor amplifier is
connected with a load resistance of 6 kO.
When a small AC signal of 15 mV is added to
the base-emitter voltage, the alternating base
current is 20 µA and the alternating collector
current is 1.8 mA. What is the voltage gain of
the amplifier?
(a) 90 (b) 640 (c) 900 (d) 720
7.
In the circuit shown, the value of ß of the
transistor is 48. If the supplied base current
Physics
500W
l
B
=200 A m
Y
V
CC
=5V
WB JEE
Engineering Entrance Exam
Solved Paper 2020
Page 1 of 45
Page 2


Category I (Q. Nos. 1 to 30)
Carry 1 marks each and only one option is
correct. In case of incorrect answer or any
combination of more than one answer, 1/4 mark
will be deducted.
1. The intensity of light emerging from one of
the slits in a Young’s double slit experiment
is found to be 1.5 times the intensity of light
emerging from the other slit. What will be
the approximate ratio of intensity of an
interference maximum to that of an
interference minimum?
(a) 2.25 (b) 98 (c) 5 (d) 9.9
2. In a Fraunhofer diffraction experiment, a
single slit of width 0.5 mm is illuminated by
a monochromatic light of wavelength
600 nm. The diffraction pattern is observed
on a screen at a distance of 50 cm from the
slit. What will be the linear separation of the
first order minima?
(a) 1.0 mm (b) 1.1 mm
(c) 0.6 mm (d) 1.2 mm
3. If R is the Rydberg constant in cm
-1
, then
hydrogen atom does not emit any radiation
of wavelength in the range of
(a)
1
R
to
4
3R
cm (b)
7
5R
to
19
5R
cm
(c)
4
R
to
36
5R
cm (d)
9
R
to
144
7R
cm
4. A nucleus X emits a ß-particle to produce a
nucleus Y. If their atomic masses are M
x
and
M
y
respectively, then the maximum energy of
the ß-particle emitted is (where, m
e
is the
mass of an electron and c is the velocity of
light)
(a)( ) M M m c
x y e
- -
2
(b)( ) M M m c
x y e
- +
2
(c)( ) M M c
x y
-
2
(d)( ) M M m c
x y e
- -2
2
5. For nuclei with mass number close to 119
and 238, the binding energies per nucleon are
approximately 7.6 MeV and 8.6 MeV,
respectively. If a nucleus of mass number 238
breaks into two nuclei of nearly equal masses,
what will be the approximate amount of
energy released in the process of fission?
(a) 214 MeV (b) 119 MeV
(c) 2047 MeV (d) 1142 MeV
6. A common emitter transistor amplifier is
connected with a load resistance of 6 kO.
When a small AC signal of 15 mV is added to
the base-emitter voltage, the alternating base
current is 20 µA and the alternating collector
current is 1.8 mA. What is the voltage gain of
the amplifier?
(a) 90 (b) 640 (c) 900 (d) 720
7.
In the circuit shown, the value of ß of the
transistor is 48. If the supplied base current
Physics
500W
l
B
=200 A m
Y
V
CC
=5V
WB JEE
Engineering Entrance Exam
Solved Paper 2020
Page 1 of 45
is 200 µA, what is the voltage at the terminal
Y?
(a) 0.2 V (b) 0.5 V (c) 4 V (d) 4.8 V
8. The frequency ? of the radiation emitted by
an atom when an electron jumps from one
orbit to another is given by ? d = k E, where k
is a constant and dE is the change in energy
level due to the transition. Then, dimension
of k is
(a)[ML T
2 2 -
]
(b) the same dimension of angular momentum
(c)[ML T
2 1 -
]
(d)[M L T]
1 –2 -
9. Consider the vectorsA i j k = + -
$ $ $
,
B i j k = - + 2
$ $ $
andC i 2j 2k = - +
1
5
(
$ $ $
). What is
the value ofC ·( ) A B × ?
(a) 1 (b) 0
(c) 3 2 (d)18 5
10. A fighter plane, flying horizontally with a
speed 360 km/h at an altitude of 500 m drops
a bomb for a target straight ahead of it on the
ground. The bomb should be dropped at
what approximate distance ahead of the
target? Assume that acceleration due to
gravity( ) g is 10 ms
-2
. Also, neglect air drag.
(a) 1000 m (b) 50 5 m
(c) 500 5 m (d) 866 m
11. A block of mass m rests on a horizontal table
with a coefficient of static friction µ. What
minimum force must be applied on the block
to drag it on the table?
(a)
µ
µ 1
2
+
mg (b)
µ
µ
-
+
1
1
mg
(c)
µ
µ 1
2
-
mg (d) µ mg
12. A tennis ball hits the floor with a speed v at
an angle ? with the normal to the floor. If the
collision is inelastic and the coefficient of
restitution is e, what will be the angle of
reflection?
(a) tan
tan
- ?
?
?
?
?
?
1
?
e
(b)sin
sin
- ?
?
?
?
?
?
1
?
e
(c) ?e (d) ?
e
e
2
1 +
13. The bob of a swinging second pendulum (one
whose time period is 2 s) has a small speed v
0
at its lowest point. Its height from this lowest
point 2.25 s after passing through it, is given
by
(a)
v
g
0
2
2
(b)
v
g
0
2
(c)
v
g
0
2
4
(d)
9
4
0
2
v
g
14. A steel and a brass wire, each of length 50 cm
and cross-sectional area 0.005 cm
2
hang from
a ceiling and are 15 cm apart. Lower ends of
the wires are attached to a light horizontal
bar. A suitable downward load is applied to
the bar, so that each of the wires extends in
length by 0.1 cm. At what distance from the
steel wire, the load must be applied?
[Young’s modulus of steel = × 2 10
12
dyne/cm
2
and that of brass = × 1 10
12
dyne/cm
2
]
(a) 7.5 cm (b) 5 cm
(c) 10 cm (d) 3 cm
15. Which of the following diagrams correctly
shows the relation between the terminal
velocity v
T
of a spherical body falling in a
liquid and viscosity ? of the liquid?
16. An ideal gas undergoes the cyclic process abca
as shown in the given p V - diagram.
(a) (b)
(c) (d)
v
T
v
T
v
T
v
T
h
h
h
h
p
V
c
a
b
Page 2 of 45
Page 3


Category I (Q. Nos. 1 to 30)
Carry 1 marks each and only one option is
correct. In case of incorrect answer or any
combination of more than one answer, 1/4 mark
will be deducted.
1. The intensity of light emerging from one of
the slits in a Young’s double slit experiment
is found to be 1.5 times the intensity of light
emerging from the other slit. What will be
the approximate ratio of intensity of an
interference maximum to that of an
interference minimum?
(a) 2.25 (b) 98 (c) 5 (d) 9.9
2. In a Fraunhofer diffraction experiment, a
single slit of width 0.5 mm is illuminated by
a monochromatic light of wavelength
600 nm. The diffraction pattern is observed
on a screen at a distance of 50 cm from the
slit. What will be the linear separation of the
first order minima?
(a) 1.0 mm (b) 1.1 mm
(c) 0.6 mm (d) 1.2 mm
3. If R is the Rydberg constant in cm
-1
, then
hydrogen atom does not emit any radiation
of wavelength in the range of
(a)
1
R
to
4
3R
cm (b)
7
5R
to
19
5R
cm
(c)
4
R
to
36
5R
cm (d)
9
R
to
144
7R
cm
4. A nucleus X emits a ß-particle to produce a
nucleus Y. If their atomic masses are M
x
and
M
y
respectively, then the maximum energy of
the ß-particle emitted is (where, m
e
is the
mass of an electron and c is the velocity of
light)
(a)( ) M M m c
x y e
- -
2
(b)( ) M M m c
x y e
- +
2
(c)( ) M M c
x y
-
2
(d)( ) M M m c
x y e
- -2
2
5. For nuclei with mass number close to 119
and 238, the binding energies per nucleon are
approximately 7.6 MeV and 8.6 MeV,
respectively. If a nucleus of mass number 238
breaks into two nuclei of nearly equal masses,
what will be the approximate amount of
energy released in the process of fission?
(a) 214 MeV (b) 119 MeV
(c) 2047 MeV (d) 1142 MeV
6. A common emitter transistor amplifier is
connected with a load resistance of 6 kO.
When a small AC signal of 15 mV is added to
the base-emitter voltage, the alternating base
current is 20 µA and the alternating collector
current is 1.8 mA. What is the voltage gain of
the amplifier?
(a) 90 (b) 640 (c) 900 (d) 720
7.
In the circuit shown, the value of ß of the
transistor is 48. If the supplied base current
Physics
500W
l
B
=200 A m
Y
V
CC
=5V
WB JEE
Engineering Entrance Exam
Solved Paper 2020
Page 1 of 45
is 200 µA, what is the voltage at the terminal
Y?
(a) 0.2 V (b) 0.5 V (c) 4 V (d) 4.8 V
8. The frequency ? of the radiation emitted by
an atom when an electron jumps from one
orbit to another is given by ? d = k E, where k
is a constant and dE is the change in energy
level due to the transition. Then, dimension
of k is
(a)[ML T
2 2 -
]
(b) the same dimension of angular momentum
(c)[ML T
2 1 -
]
(d)[M L T]
1 –2 -
9. Consider the vectorsA i j k = + -
$ $ $
,
B i j k = - + 2
$ $ $
andC i 2j 2k = - +
1
5
(
$ $ $
). What is
the value ofC ·( ) A B × ?
(a) 1 (b) 0
(c) 3 2 (d)18 5
10. A fighter plane, flying horizontally with a
speed 360 km/h at an altitude of 500 m drops
a bomb for a target straight ahead of it on the
ground. The bomb should be dropped at
what approximate distance ahead of the
target? Assume that acceleration due to
gravity( ) g is 10 ms
-2
. Also, neglect air drag.
(a) 1000 m (b) 50 5 m
(c) 500 5 m (d) 866 m
11. A block of mass m rests on a horizontal table
with a coefficient of static friction µ. What
minimum force must be applied on the block
to drag it on the table?
(a)
µ
µ 1
2
+
mg (b)
µ
µ
-
+
1
1
mg
(c)
µ
µ 1
2
-
mg (d) µ mg
12. A tennis ball hits the floor with a speed v at
an angle ? with the normal to the floor. If the
collision is inelastic and the coefficient of
restitution is e, what will be the angle of
reflection?
(a) tan
tan
- ?
?
?
?
?
?
1
?
e
(b)sin
sin
- ?
?
?
?
?
?
1
?
e
(c) ?e (d) ?
e
e
2
1 +
13. The bob of a swinging second pendulum (one
whose time period is 2 s) has a small speed v
0
at its lowest point. Its height from this lowest
point 2.25 s after passing through it, is given
by
(a)
v
g
0
2
2
(b)
v
g
0
2
(c)
v
g
0
2
4
(d)
9
4
0
2
v
g
14. A steel and a brass wire, each of length 50 cm
and cross-sectional area 0.005 cm
2
hang from
a ceiling and are 15 cm apart. Lower ends of
the wires are attached to a light horizontal
bar. A suitable downward load is applied to
the bar, so that each of the wires extends in
length by 0.1 cm. At what distance from the
steel wire, the load must be applied?
[Young’s modulus of steel = × 2 10
12
dyne/cm
2
and that of brass = × 1 10
12
dyne/cm
2
]
(a) 7.5 cm (b) 5 cm
(c) 10 cm (d) 3 cm
15. Which of the following diagrams correctly
shows the relation between the terminal
velocity v
T
of a spherical body falling in a
liquid and viscosity ? of the liquid?
16. An ideal gas undergoes the cyclic process abca
as shown in the given p V - diagram.
(a) (b)
(c) (d)
v
T
v
T
v
T
v
T
h
h
h
h
p
V
c
a
b
Page 2 of 45
It rejects 50 J of heat during ab and absorbs
80 J of heat during ca. During bc, there is no
transfer of heat and 40 J of work is done by
the gas. What should be the area of the
closed curve abca?
(a) 30 J (b) 40 J (c) 10 J (d) 90 J
17. A container AB in the shape of a rectangular
parallelopiped of length 5 m is divided
internally by a movable partition P as shown
in the figure.
The left compartment is filled with a given
mass of an ideal gas of molar mass 32 while
the right compartment is filled with an equal
mass of another ideal gas of molar mass 18 at
same temperature. What will be the distance
of P from the left wall A when equilibrium is
established?
(a) 2.5 m (b) 1.8 m (c) 3.2 m (d) 2.1 m
18. When 100 g of boiling water at 100°C is
added into a calorimeter containing 300 g of
cold water at 10°C, temperature of the
mixture becomes 20°C. Then, a metallic block
of mass 1 kg at 10°C is dipped into the
mixture in the calorimeter. After reaching
thermal equilibrium, the final temperature
becomes 19°C. What is the specific heat of
the metal in CGS unit?
(a) 0.01 (b) 0.3 (c) 0.09 (d) 0.1
19. As shown in the figure, a point charge
q
1
6
1 10 = + ×
-
C is placed at the origin in
xy-plane and another point charge
q
2
6
3 10 = + ×
-
C is placed at the coordinate
(10, 0).
In that case, which of the following graph(s)
shows most correctly the electric field vector
in E
x
in x-direction?
20. Four identical point masses, each of mass m
and carrying charge + q are placed at the
corners of a square of sides a on a frictionless
plane surface. If the particles are released
simultaneously, the kinetic energy of the
system when they are infinitely far apart is
(a)
q
a
2
2 2 1 ( ) + (b)
q
a
2
2 2 ( ) +
(c)
q
a
2
2 4 ( ) + (d)
q
a
2
2 1 ( ) +
21. A very long charged solid cylinder of radius a
contains a uniform charge density ?.
Dielectric constant of the material of the
cylinder is K. What will be the magnitude of
electric field at a radial distance x( ) x a < from
the axis of the cylinder?
(a) ?
e
x
0
(b) ?
e
x
k 2
0
(c) ?
e
x
a
2
0
2
(d) ?
x
k 2
22. A galvanometer can be converted to a
voltmeter of full scale deflection V
0
by
connecting a series resistance R
1
and can be
converted to an ammeter of full scale
deflection I
0
by connecting a shunt resistance
R
2
. What is the current flowing through the
galvanometer at its full scale deflection?
(a)
V I R
R R
0 0 2
1 2
-
-
(b)
V I R
R R
0 0 2
1 2
+
+
(c)
V I R
R R
0 0 1
2 1
-
-
(d)
V I R
R R
0 0 1
1 2
+
+
E
x
E
x
E
x
E
x
x
x
x
x
O O
O O
(10,0)
(10,0)
(10,0) (10,0)
(d) (c)
(b) (a)
B P A
5m
Y
X
q
1
q
2
(10,0)
Page 3 of 45
Page 4


Category I (Q. Nos. 1 to 30)
Carry 1 marks each and only one option is
correct. In case of incorrect answer or any
combination of more than one answer, 1/4 mark
will be deducted.
1. The intensity of light emerging from one of
the slits in a Young’s double slit experiment
is found to be 1.5 times the intensity of light
emerging from the other slit. What will be
the approximate ratio of intensity of an
interference maximum to that of an
interference minimum?
(a) 2.25 (b) 98 (c) 5 (d) 9.9
2. In a Fraunhofer diffraction experiment, a
single slit of width 0.5 mm is illuminated by
a monochromatic light of wavelength
600 nm. The diffraction pattern is observed
on a screen at a distance of 50 cm from the
slit. What will be the linear separation of the
first order minima?
(a) 1.0 mm (b) 1.1 mm
(c) 0.6 mm (d) 1.2 mm
3. If R is the Rydberg constant in cm
-1
, then
hydrogen atom does not emit any radiation
of wavelength in the range of
(a)
1
R
to
4
3R
cm (b)
7
5R
to
19
5R
cm
(c)
4
R
to
36
5R
cm (d)
9
R
to
144
7R
cm
4. A nucleus X emits a ß-particle to produce a
nucleus Y. If their atomic masses are M
x
and
M
y
respectively, then the maximum energy of
the ß-particle emitted is (where, m
e
is the
mass of an electron and c is the velocity of
light)
(a)( ) M M m c
x y e
- -
2
(b)( ) M M m c
x y e
- +
2
(c)( ) M M c
x y
-
2
(d)( ) M M m c
x y e
- -2
2
5. For nuclei with mass number close to 119
and 238, the binding energies per nucleon are
approximately 7.6 MeV and 8.6 MeV,
respectively. If a nucleus of mass number 238
breaks into two nuclei of nearly equal masses,
what will be the approximate amount of
energy released in the process of fission?
(a) 214 MeV (b) 119 MeV
(c) 2047 MeV (d) 1142 MeV
6. A common emitter transistor amplifier is
connected with a load resistance of 6 kO.
When a small AC signal of 15 mV is added to
the base-emitter voltage, the alternating base
current is 20 µA and the alternating collector
current is 1.8 mA. What is the voltage gain of
the amplifier?
(a) 90 (b) 640 (c) 900 (d) 720
7.
In the circuit shown, the value of ß of the
transistor is 48. If the supplied base current
Physics
500W
l
B
=200 A m
Y
V
CC
=5V
WB JEE
Engineering Entrance Exam
Solved Paper 2020
Page 1 of 45
is 200 µA, what is the voltage at the terminal
Y?
(a) 0.2 V (b) 0.5 V (c) 4 V (d) 4.8 V
8. The frequency ? of the radiation emitted by
an atom when an electron jumps from one
orbit to another is given by ? d = k E, where k
is a constant and dE is the change in energy
level due to the transition. Then, dimension
of k is
(a)[ML T
2 2 -
]
(b) the same dimension of angular momentum
(c)[ML T
2 1 -
]
(d)[M L T]
1 –2 -
9. Consider the vectorsA i j k = + -
$ $ $
,
B i j k = - + 2
$ $ $
andC i 2j 2k = - +
1
5
(
$ $ $
). What is
the value ofC ·( ) A B × ?
(a) 1 (b) 0
(c) 3 2 (d)18 5
10. A fighter plane, flying horizontally with a
speed 360 km/h at an altitude of 500 m drops
a bomb for a target straight ahead of it on the
ground. The bomb should be dropped at
what approximate distance ahead of the
target? Assume that acceleration due to
gravity( ) g is 10 ms
-2
. Also, neglect air drag.
(a) 1000 m (b) 50 5 m
(c) 500 5 m (d) 866 m
11. A block of mass m rests on a horizontal table
with a coefficient of static friction µ. What
minimum force must be applied on the block
to drag it on the table?
(a)
µ
µ 1
2
+
mg (b)
µ
µ
-
+
1
1
mg
(c)
µ
µ 1
2
-
mg (d) µ mg
12. A tennis ball hits the floor with a speed v at
an angle ? with the normal to the floor. If the
collision is inelastic and the coefficient of
restitution is e, what will be the angle of
reflection?
(a) tan
tan
- ?
?
?
?
?
?
1
?
e
(b)sin
sin
- ?
?
?
?
?
?
1
?
e
(c) ?e (d) ?
e
e
2
1 +
13. The bob of a swinging second pendulum (one
whose time period is 2 s) has a small speed v
0
at its lowest point. Its height from this lowest
point 2.25 s after passing through it, is given
by
(a)
v
g
0
2
2
(b)
v
g
0
2
(c)
v
g
0
2
4
(d)
9
4
0
2
v
g
14. A steel and a brass wire, each of length 50 cm
and cross-sectional area 0.005 cm
2
hang from
a ceiling and are 15 cm apart. Lower ends of
the wires are attached to a light horizontal
bar. A suitable downward load is applied to
the bar, so that each of the wires extends in
length by 0.1 cm. At what distance from the
steel wire, the load must be applied?
[Young’s modulus of steel = × 2 10
12
dyne/cm
2
and that of brass = × 1 10
12
dyne/cm
2
]
(a) 7.5 cm (b) 5 cm
(c) 10 cm (d) 3 cm
15. Which of the following diagrams correctly
shows the relation between the terminal
velocity v
T
of a spherical body falling in a
liquid and viscosity ? of the liquid?
16. An ideal gas undergoes the cyclic process abca
as shown in the given p V - diagram.
(a) (b)
(c) (d)
v
T
v
T
v
T
v
T
h
h
h
h
p
V
c
a
b
Page 2 of 45
It rejects 50 J of heat during ab and absorbs
80 J of heat during ca. During bc, there is no
transfer of heat and 40 J of work is done by
the gas. What should be the area of the
closed curve abca?
(a) 30 J (b) 40 J (c) 10 J (d) 90 J
17. A container AB in the shape of a rectangular
parallelopiped of length 5 m is divided
internally by a movable partition P as shown
in the figure.
The left compartment is filled with a given
mass of an ideal gas of molar mass 32 while
the right compartment is filled with an equal
mass of another ideal gas of molar mass 18 at
same temperature. What will be the distance
of P from the left wall A when equilibrium is
established?
(a) 2.5 m (b) 1.8 m (c) 3.2 m (d) 2.1 m
18. When 100 g of boiling water at 100°C is
added into a calorimeter containing 300 g of
cold water at 10°C, temperature of the
mixture becomes 20°C. Then, a metallic block
of mass 1 kg at 10°C is dipped into the
mixture in the calorimeter. After reaching
thermal equilibrium, the final temperature
becomes 19°C. What is the specific heat of
the metal in CGS unit?
(a) 0.01 (b) 0.3 (c) 0.09 (d) 0.1
19. As shown in the figure, a point charge
q
1
6
1 10 = + ×
-
C is placed at the origin in
xy-plane and another point charge
q
2
6
3 10 = + ×
-
C is placed at the coordinate
(10, 0).
In that case, which of the following graph(s)
shows most correctly the electric field vector
in E
x
in x-direction?
20. Four identical point masses, each of mass m
and carrying charge + q are placed at the
corners of a square of sides a on a frictionless
plane surface. If the particles are released
simultaneously, the kinetic energy of the
system when they are infinitely far apart is
(a)
q
a
2
2 2 1 ( ) + (b)
q
a
2
2 2 ( ) +
(c)
q
a
2
2 4 ( ) + (d)
q
a
2
2 1 ( ) +
21. A very long charged solid cylinder of radius a
contains a uniform charge density ?.
Dielectric constant of the material of the
cylinder is K. What will be the magnitude of
electric field at a radial distance x( ) x a < from
the axis of the cylinder?
(a) ?
e
x
0
(b) ?
e
x
k 2
0
(c) ?
e
x
a
2
0
2
(d) ?
x
k 2
22. A galvanometer can be converted to a
voltmeter of full scale deflection V
0
by
connecting a series resistance R
1
and can be
converted to an ammeter of full scale
deflection I
0
by connecting a shunt resistance
R
2
. What is the current flowing through the
galvanometer at its full scale deflection?
(a)
V I R
R R
0 0 2
1 2
-
-
(b)
V I R
R R
0 0 2
1 2
+
+
(c)
V I R
R R
0 0 1
2 1
-
-
(d)
V I R
R R
0 0 1
1 2
+
+
E
x
E
x
E
x
E
x
x
x
x
x
O O
O O
(10,0)
(10,0)
(10,0) (10,0)
(d) (c)
(b) (a)
B P A
5m
Y
X
q
1
q
2
(10,0)
Page 3 of 45
23.
As shown in the figure, a single conducting
wire is bent to form a loop in the form of a
circle of radius r concentrically inside a
square of side a, where a r : : =8 p. A battery
B drives a current through the wire. If the
battery B and the gapG are of negligible sizes,
determine the strength of magnetic field at
the common centre O.
(a)
µ
p
0
2
2 2 1
I
a
( ) - (b)
µ
p
0
2
2 1
I
a
( ) +
(c)
µ
p
0
2 2 2 1
I
a
( ) + (d)
µ
p
0
2 2 2 1
I
a
( ) -
24.
As shown in the figure, a wire is bent to form
a D-shaped closed loop, carrying current I,
where the curved part is a semi-circle of
radius R. The loop is placed in a uniform
magnetic fieldB, which is directed into the
plane of the paper. The magnetic force felt by
the closed loop is
(a) zero (b) IRB (c) 2IRB (d)
1
2
IRB
25.
What will be the equivalent resistance
between the terminals A and B of the infinite
resistive network shown in the figure?
(a)
( ) 3 1
2
+ R
(b)
( ) 3 1
2
- R
(c) 3
2
R
(d)( ) 3 1 + R
26.
When a DC voltage is applied at the two ends
of a circuit kept in a closed box, it is observed
that the current gradually increases from
zero to a certain value and then remains
constant. What do you think that the circuit
contains?
(a) A resistor alone
(b) A capacitor alone
(c) A resistor and an inductor in series
(d) A resistor and a capacitor in series
27. Consider the circuit shown.
If all the cells have negligible internal
resistance, what will be the current through
the2O resistor when steady state is reached?
(a) 0.66 A (b) 0.29 A (c) 0 A (d) 0.14 A
28. Consider a conducting wire of length L bent
in the form of a circle of radius R and another
conductor of length a( ) a R < < is bent in the
form of a square. The two loops are then
placed in same plane such that the square
loop is exactly at the centre of the circular
loop. What will be the mutual inductance
between the two loops?
(a) µ
p
0
2
a
L
(b) µ
p
0
2
16
a
L
(c) µ
p
0
2
4
a
L
(d) µ
p
0
2
4
a
L
29. An object, is placed 60 cm in front of a
convex mirror of focal length 30 cm. A plane
mirror is now placed facing the object in
between the object and the convex mirror
such that it covers lower half of the convex
mirror. What should be the distance of the
2R 2R 2R
A
B
R R R
A
I
t
2 F µ
2V 2V
2V
2W 8W
4W
8W
R
O
×
×
×
×
×
×
×
×
×
×
×
×
×
×
×
×
×
×
O
r
a G
B
a
Page 4 of 45
Page 5


Category I (Q. Nos. 1 to 30)
Carry 1 marks each and only one option is
correct. In case of incorrect answer or any
combination of more than one answer, 1/4 mark
will be deducted.
1. The intensity of light emerging from one of
the slits in a Young’s double slit experiment
is found to be 1.5 times the intensity of light
emerging from the other slit. What will be
the approximate ratio of intensity of an
interference maximum to that of an
interference minimum?
(a) 2.25 (b) 98 (c) 5 (d) 9.9
2. In a Fraunhofer diffraction experiment, a
single slit of width 0.5 mm is illuminated by
a monochromatic light of wavelength
600 nm. The diffraction pattern is observed
on a screen at a distance of 50 cm from the
slit. What will be the linear separation of the
first order minima?
(a) 1.0 mm (b) 1.1 mm
(c) 0.6 mm (d) 1.2 mm
3. If R is the Rydberg constant in cm
-1
, then
hydrogen atom does not emit any radiation
of wavelength in the range of
(a)
1
R
to
4
3R
cm (b)
7
5R
to
19
5R
cm
(c)
4
R
to
36
5R
cm (d)
9
R
to
144
7R
cm
4. A nucleus X emits a ß-particle to produce a
nucleus Y. If their atomic masses are M
x
and
M
y
respectively, then the maximum energy of
the ß-particle emitted is (where, m
e
is the
mass of an electron and c is the velocity of
light)
(a)( ) M M m c
x y e
- -
2
(b)( ) M M m c
x y e
- +
2
(c)( ) M M c
x y
-
2
(d)( ) M M m c
x y e
- -2
2
5. For nuclei with mass number close to 119
and 238, the binding energies per nucleon are
approximately 7.6 MeV and 8.6 MeV,
respectively. If a nucleus of mass number 238
breaks into two nuclei of nearly equal masses,
what will be the approximate amount of
energy released in the process of fission?
(a) 214 MeV (b) 119 MeV
(c) 2047 MeV (d) 1142 MeV
6. A common emitter transistor amplifier is
connected with a load resistance of 6 kO.
When a small AC signal of 15 mV is added to
the base-emitter voltage, the alternating base
current is 20 µA and the alternating collector
current is 1.8 mA. What is the voltage gain of
the amplifier?
(a) 90 (b) 640 (c) 900 (d) 720
7.
In the circuit shown, the value of ß of the
transistor is 48. If the supplied base current
Physics
500W
l
B
=200 A m
Y
V
CC
=5V
WB JEE
Engineering Entrance Exam
Solved Paper 2020
Page 1 of 45
is 200 µA, what is the voltage at the terminal
Y?
(a) 0.2 V (b) 0.5 V (c) 4 V (d) 4.8 V
8. The frequency ? of the radiation emitted by
an atom when an electron jumps from one
orbit to another is given by ? d = k E, where k
is a constant and dE is the change in energy
level due to the transition. Then, dimension
of k is
(a)[ML T
2 2 -
]
(b) the same dimension of angular momentum
(c)[ML T
2 1 -
]
(d)[M L T]
1 –2 -
9. Consider the vectorsA i j k = + -
$ $ $
,
B i j k = - + 2
$ $ $
andC i 2j 2k = - +
1
5
(
$ $ $
). What is
the value ofC ·( ) A B × ?
(a) 1 (b) 0
(c) 3 2 (d)18 5
10. A fighter plane, flying horizontally with a
speed 360 km/h at an altitude of 500 m drops
a bomb for a target straight ahead of it on the
ground. The bomb should be dropped at
what approximate distance ahead of the
target? Assume that acceleration due to
gravity( ) g is 10 ms
-2
. Also, neglect air drag.
(a) 1000 m (b) 50 5 m
(c) 500 5 m (d) 866 m
11. A block of mass m rests on a horizontal table
with a coefficient of static friction µ. What
minimum force must be applied on the block
to drag it on the table?
(a)
µ
µ 1
2
+
mg (b)
µ
µ
-
+
1
1
mg
(c)
µ
µ 1
2
-
mg (d) µ mg
12. A tennis ball hits the floor with a speed v at
an angle ? with the normal to the floor. If the
collision is inelastic and the coefficient of
restitution is e, what will be the angle of
reflection?
(a) tan
tan
- ?
?
?
?
?
?
1
?
e
(b)sin
sin
- ?
?
?
?
?
?
1
?
e
(c) ?e (d) ?
e
e
2
1 +
13. The bob of a swinging second pendulum (one
whose time period is 2 s) has a small speed v
0
at its lowest point. Its height from this lowest
point 2.25 s after passing through it, is given
by
(a)
v
g
0
2
2
(b)
v
g
0
2
(c)
v
g
0
2
4
(d)
9
4
0
2
v
g
14. A steel and a brass wire, each of length 50 cm
and cross-sectional area 0.005 cm
2
hang from
a ceiling and are 15 cm apart. Lower ends of
the wires are attached to a light horizontal
bar. A suitable downward load is applied to
the bar, so that each of the wires extends in
length by 0.1 cm. At what distance from the
steel wire, the load must be applied?
[Young’s modulus of steel = × 2 10
12
dyne/cm
2
and that of brass = × 1 10
12
dyne/cm
2
]
(a) 7.5 cm (b) 5 cm
(c) 10 cm (d) 3 cm
15. Which of the following diagrams correctly
shows the relation between the terminal
velocity v
T
of a spherical body falling in a
liquid and viscosity ? of the liquid?
16. An ideal gas undergoes the cyclic process abca
as shown in the given p V - diagram.
(a) (b)
(c) (d)
v
T
v
T
v
T
v
T
h
h
h
h
p
V
c
a
b
Page 2 of 45
It rejects 50 J of heat during ab and absorbs
80 J of heat during ca. During bc, there is no
transfer of heat and 40 J of work is done by
the gas. What should be the area of the
closed curve abca?
(a) 30 J (b) 40 J (c) 10 J (d) 90 J
17. A container AB in the shape of a rectangular
parallelopiped of length 5 m is divided
internally by a movable partition P as shown
in the figure.
The left compartment is filled with a given
mass of an ideal gas of molar mass 32 while
the right compartment is filled with an equal
mass of another ideal gas of molar mass 18 at
same temperature. What will be the distance
of P from the left wall A when equilibrium is
established?
(a) 2.5 m (b) 1.8 m (c) 3.2 m (d) 2.1 m
18. When 100 g of boiling water at 100°C is
added into a calorimeter containing 300 g of
cold water at 10°C, temperature of the
mixture becomes 20°C. Then, a metallic block
of mass 1 kg at 10°C is dipped into the
mixture in the calorimeter. After reaching
thermal equilibrium, the final temperature
becomes 19°C. What is the specific heat of
the metal in CGS unit?
(a) 0.01 (b) 0.3 (c) 0.09 (d) 0.1
19. As shown in the figure, a point charge
q
1
6
1 10 = + ×
-
C is placed at the origin in
xy-plane and another point charge
q
2
6
3 10 = + ×
-
C is placed at the coordinate
(10, 0).
In that case, which of the following graph(s)
shows most correctly the electric field vector
in E
x
in x-direction?
20. Four identical point masses, each of mass m
and carrying charge + q are placed at the
corners of a square of sides a on a frictionless
plane surface. If the particles are released
simultaneously, the kinetic energy of the
system when they are infinitely far apart is
(a)
q
a
2
2 2 1 ( ) + (b)
q
a
2
2 2 ( ) +
(c)
q
a
2
2 4 ( ) + (d)
q
a
2
2 1 ( ) +
21. A very long charged solid cylinder of radius a
contains a uniform charge density ?.
Dielectric constant of the material of the
cylinder is K. What will be the magnitude of
electric field at a radial distance x( ) x a < from
the axis of the cylinder?
(a) ?
e
x
0
(b) ?
e
x
k 2
0
(c) ?
e
x
a
2
0
2
(d) ?
x
k 2
22. A galvanometer can be converted to a
voltmeter of full scale deflection V
0
by
connecting a series resistance R
1
and can be
converted to an ammeter of full scale
deflection I
0
by connecting a shunt resistance
R
2
. What is the current flowing through the
galvanometer at its full scale deflection?
(a)
V I R
R R
0 0 2
1 2
-
-
(b)
V I R
R R
0 0 2
1 2
+
+
(c)
V I R
R R
0 0 1
2 1
-
-
(d)
V I R
R R
0 0 1
1 2
+
+
E
x
E
x
E
x
E
x
x
x
x
x
O O
O O
(10,0)
(10,0)
(10,0) (10,0)
(d) (c)
(b) (a)
B P A
5m
Y
X
q
1
q
2
(10,0)
Page 3 of 45
23.
As shown in the figure, a single conducting
wire is bent to form a loop in the form of a
circle of radius r concentrically inside a
square of side a, where a r : : =8 p. A battery
B drives a current through the wire. If the
battery B and the gapG are of negligible sizes,
determine the strength of magnetic field at
the common centre O.
(a)
µ
p
0
2
2 2 1
I
a
( ) - (b)
µ
p
0
2
2 1
I
a
( ) +
(c)
µ
p
0
2 2 2 1
I
a
( ) + (d)
µ
p
0
2 2 2 1
I
a
( ) -
24.
As shown in the figure, a wire is bent to form
a D-shaped closed loop, carrying current I,
where the curved part is a semi-circle of
radius R. The loop is placed in a uniform
magnetic fieldB, which is directed into the
plane of the paper. The magnetic force felt by
the closed loop is
(a) zero (b) IRB (c) 2IRB (d)
1
2
IRB
25.
What will be the equivalent resistance
between the terminals A and B of the infinite
resistive network shown in the figure?
(a)
( ) 3 1
2
+ R
(b)
( ) 3 1
2
- R
(c) 3
2
R
(d)( ) 3 1 + R
26.
When a DC voltage is applied at the two ends
of a circuit kept in a closed box, it is observed
that the current gradually increases from
zero to a certain value and then remains
constant. What do you think that the circuit
contains?
(a) A resistor alone
(b) A capacitor alone
(c) A resistor and an inductor in series
(d) A resistor and a capacitor in series
27. Consider the circuit shown.
If all the cells have negligible internal
resistance, what will be the current through
the2O resistor when steady state is reached?
(a) 0.66 A (b) 0.29 A (c) 0 A (d) 0.14 A
28. Consider a conducting wire of length L bent
in the form of a circle of radius R and another
conductor of length a( ) a R < < is bent in the
form of a square. The two loops are then
placed in same plane such that the square
loop is exactly at the centre of the circular
loop. What will be the mutual inductance
between the two loops?
(a) µ
p
0
2
a
L
(b) µ
p
0
2
16
a
L
(c) µ
p
0
2
4
a
L
(d) µ
p
0
2
4
a
L
29. An object, is placed 60 cm in front of a
convex mirror of focal length 30 cm. A plane
mirror is now placed facing the object in
between the object and the convex mirror
such that it covers lower half of the convex
mirror. What should be the distance of the
2R 2R 2R
A
B
R R R
A
I
t
2 F µ
2V 2V
2V
2W 8W
4W
8W
R
O
×
×
×
×
×
×
×
×
×
×
×
×
×
×
×
×
×
×
O
r
a G
B
a
Page 4 of 45
plane mirror from the object, so that there
will be no parallax between the images
formed by the two mirrors?
(a) 40 cm (b) 30 cm (c) 20 cm (d) 15 cm
30. A thin convex lens is placed just above an
empty vessel of depth 80 cm. The image of a
coin kept at the bottom of the vessel is thus
formed 20 cm above the lens. If now water is
poured in the vessel upto a height of 64 cm,
what will be the approximate new position of
the image? Assume that refractive index of
water is 4/3.
(a) 21.33 cm, above the lens
(b) 6.67 cm, below the lens
(c) 33.67 cm, above the lens
(d) 24 cm, above the lens
Category II (Q. Nos. 31 to 35)
Carry 2 marks each and only one option is correct.
In case of incorrect answer or any combination of
more than one answer, 1/2 mark will be deducted.
31. A conducting circular loop of resistance20 O
and cross-sectional area20 10
2
×
-
m
2
is
placed perpendicular to a spatially uniform
magnetic fieldB, which varies with time t as
B =2 50 sin( ) pt T. Find the net charge flowing
through the loop in 20 ms starting from t =0.
(a) 0.5 C (b) 0.2 C (c) 0 C (d) 0.14 C
32. A pair of parallel metal plates are kept with a
separation d. One plate is at a potential + V
and the other is at ground potential. A
narrow beam of electrons enters the space
between the plates with a velocity v
0
and in
a direction parallel to the plates. What will be
the angle of the beam with the plates after it
travels an axial distance L?
(a) tan
-
?
?
?
?
?
?
1
0
eVL
mdv
(b) tan
-
?
?
?
?
?
?
?
?
1
0
2
eVL
mdv
(c)sin
-
?
?
?
?
?
?
1
0
eVL
mdv
(d)cos
-
?
?
?
?
?
?
?
?
1
0
2
eVL
mdv
33. A metallic block of mass 20 kg is dragged
with a uniform velocity of 0.5 ms
-1
on a
horizontal table for 2.1 s. The coefficient of
static friction between the block and the
table is 0.10. What will be the maximum
possible rise in temperature of the metal
block, if the specific heat of the block is 0.1
CGS unit? Assume g =
-
10
2
ms and uniform
rise in temperature throughout the whole
block. [Ignore absorption of heat by the
table]
(a) 0.0025°C (b) 0.025°C
(c) 0.001°C (d) 0.05°C
34. Consider an engine that absorbs 130 cal of
heat from a hot reservoir and delivers 30 cal
heat to a cold reservoir in each cycle. The
engine also consumes 2 J energy in each
cycle to overcome friction. If the engine
works at 90 cycles per minute, what will be
the maximum power delivered to the load?
[Assume the thermal equivalent of heat is
4.2 J/cal]
(a) 816 W (b) 819 W
(c) 627 W (d) 630 W
35. Two pith balls, each carrying charge + q are
hung from a hook by two strings. It is found
that when each charge is tripled, angle
between the strings double. What was the
initial angle between the strings?
(a) 30° (b) 60° (c) 45° (d) 90°
Category III (Q. Nos. 36 to 40)
Carry 2 marks each and one or more option(s)
is/are correct. If all correct answers are not marked
and also no incorrect answer is marked then score
= × 2 number of correct answers marked ÷ actual
number of correct answers. If any wrong option is
marked or if any combination including a wrong
option is marked, the answer will be considered
wrong, but there is no negative marking for the
same and zero marks will be awarded.
36. A point source of light is used in an
experiment of photoelectric effects. If the
distance between the source and the
photoelectric surface is doubled, which of the
following may result?
(a) Stopping potential will be halved.
(b) Photoelectric current will decrease.
(c) Maximum kinetic energy of photoelectrons will
decrease.
(d) Stopping potential will increase slightly.
37. Two metallic spheres of equal outer radii are
found to have same moment of inertia about
Page 5 of 45