JEE Mains 24 Feb 2021 Question Paper Shift 2 | JEE Main & Advanced Previous Year Papers PDF Download

 Page 1


 
 
 
1. Zener breakdown occurs in a p-n junction having p and n both : 
 (1) lightly doped and have wide depletion layer. 
 (2) heavily doped andhave narrow depletion layer. 
 (3) heavily doped and have wide depletion layer. 
 (4) lightly doped and have narrow depletion layer. 
Ans. (2) 
Sol. The zener breakdown occurs in the heavily doped p-n junction diode. Heavily doped p-n 
junction diodes have narrow depletion region. 
 
2. According to Bohr atom model, in which of the following transitions will the frequency be 
maximum? 
 (1)n=2 to n=1 (2)n=4 to n =3 (3)n=5 to n=4 (4)n=3 to n=2 
Ans. (1) 
Sol. 
  
5 
4 
3 
2 
1 
?E=hf 
 
 f is more for transition from n = 2 to n = 1. 
 
3. An X-ray tube is operated at 1.24 million volt. The shortest wavelength of the produced photon 
will be : 
 (1) 10
-2
 nm (2)10
-3
 nm (3)10
-4
 nm (4)10
-1
 nm 
Ans. (2) 
Sol. 
min
hc
eV
? ? 
 
min
6
1240nm eV
1.24 10
?
? ?
?
 
 
3
min
10 nm
?
? ? 
 
4. On the basis of kinetic theory of gases, the gas exerts pressure because its molecules: 
 (1) suffer change in momentum when impinge on the walls of container. 
 (2) continuously stick to the walls of container. 
 (3) continuously lose their energy till it reaches wall. 
 (4) are attracted by the walls of container. 
Ans. (1) 
Sol. On the basis of kinetic theory of gases, the gas pressure is due to the molecules suffering 
change in momentum when impinge on the walls of container. 
 
24
th
 Feb. 2021 | Shift - 2
PHYSICS
Page 2


 
 
 
1. Zener breakdown occurs in a p-n junction having p and n both : 
 (1) lightly doped and have wide depletion layer. 
 (2) heavily doped andhave narrow depletion layer. 
 (3) heavily doped and have wide depletion layer. 
 (4) lightly doped and have narrow depletion layer. 
Ans. (2) 
Sol. The zener breakdown occurs in the heavily doped p-n junction diode. Heavily doped p-n 
junction diodes have narrow depletion region. 
 
2. According to Bohr atom model, in which of the following transitions will the frequency be 
maximum? 
 (1)n=2 to n=1 (2)n=4 to n =3 (3)n=5 to n=4 (4)n=3 to n=2 
Ans. (1) 
Sol. 
  
5 
4 
3 
2 
1 
?E=hf 
 
 f is more for transition from n = 2 to n = 1. 
 
3. An X-ray tube is operated at 1.24 million volt. The shortest wavelength of the produced photon 
will be : 
 (1) 10
-2
 nm (2)10
-3
 nm (3)10
-4
 nm (4)10
-1
 nm 
Ans. (2) 
Sol. 
min
hc
eV
? ? 
 
min
6
1240nm eV
1.24 10
?
? ?
?
 
 
3
min
10 nm
?
? ? 
 
4. On the basis of kinetic theory of gases, the gas exerts pressure because its molecules: 
 (1) suffer change in momentum when impinge on the walls of container. 
 (2) continuously stick to the walls of container. 
 (3) continuously lose their energy till it reaches wall. 
 (4) are attracted by the walls of container. 
Ans. (1) 
Sol. On the basis of kinetic theory of gases, the gas pressure is due to the molecules suffering 
change in momentum when impinge on the walls of container. 
 
24
th
 Feb. 2021 | Shift - 2
PHYSICS
 
 
5. A circular hole of radius 
a
2
? ?
? ?
? ?
 is cut out of a circular disc of radius ‘a’ shown in figure. The 
centroid of the remaining circular portion with respect to point ‘O’ will be : 
 
 
y-axis
O
a
a/2
x-axis
 
 
 (1)
10
a
11
 (2)
2
a
3
 (3)
1
a
6
 (4)
5
a
6
 
 
Ans. (4) 
 
Sol. Let ? is the surface mass density of disc. 
  
y 
x 
a/2 
a
3
2
 
y 
x 
a 
 
 
2
2
com
2
2
a 3a
( a a) ( )
4 2
X
a
a
4
?
? ? ? ? ? ? ?
?
? ?
? ? ?
 
 
com
a
a 3
8
X
1
1
4
?
?
?
 
 
com
5a
8
X
3
4
?
 
 
com
5a
X
6
? 
 
 
 
 
Page 3


 
 
 
1. Zener breakdown occurs in a p-n junction having p and n both : 
 (1) lightly doped and have wide depletion layer. 
 (2) heavily doped andhave narrow depletion layer. 
 (3) heavily doped and have wide depletion layer. 
 (4) lightly doped and have narrow depletion layer. 
Ans. (2) 
Sol. The zener breakdown occurs in the heavily doped p-n junction diode. Heavily doped p-n 
junction diodes have narrow depletion region. 
 
2. According to Bohr atom model, in which of the following transitions will the frequency be 
maximum? 
 (1)n=2 to n=1 (2)n=4 to n =3 (3)n=5 to n=4 (4)n=3 to n=2 
Ans. (1) 
Sol. 
  
5 
4 
3 
2 
1 
?E=hf 
 
 f is more for transition from n = 2 to n = 1. 
 
3. An X-ray tube is operated at 1.24 million volt. The shortest wavelength of the produced photon 
will be : 
 (1) 10
-2
 nm (2)10
-3
 nm (3)10
-4
 nm (4)10
-1
 nm 
Ans. (2) 
Sol. 
min
hc
eV
? ? 
 
min
6
1240nm eV
1.24 10
?
? ?
?
 
 
3
min
10 nm
?
? ? 
 
4. On the basis of kinetic theory of gases, the gas exerts pressure because its molecules: 
 (1) suffer change in momentum when impinge on the walls of container. 
 (2) continuously stick to the walls of container. 
 (3) continuously lose their energy till it reaches wall. 
 (4) are attracted by the walls of container. 
Ans. (1) 
Sol. On the basis of kinetic theory of gases, the gas pressure is due to the molecules suffering 
change in momentum when impinge on the walls of container. 
 
24
th
 Feb. 2021 | Shift - 2
PHYSICS
 
 
5. A circular hole of radius 
a
2
? ?
? ?
? ?
 is cut out of a circular disc of radius ‘a’ shown in figure. The 
centroid of the remaining circular portion with respect to point ‘O’ will be : 
 
 
y-axis
O
a
a/2
x-axis
 
 
 (1)
10
a
11
 (2)
2
a
3
 (3)
1
a
6
 (4)
5
a
6
 
 
Ans. (4) 
 
Sol. Let ? is the surface mass density of disc. 
  
y 
x 
a/2 
a
3
2
 
y 
x 
a 
 
 
2
2
com
2
2
a 3a
( a a) ( )
4 2
X
a
a
4
?
? ? ? ? ? ? ?
?
? ?
? ? ?
 
 
com
a
a 3
8
X
1
1
4
?
?
?
 
 
com
5a
8
X
3
4
?
 
 
com
5a
X
6
? 
 
 
 
 
 
 
6. Given below are two statements : 
 Statement I : PN junction diodes can be used to function as transistor, simply by connecting 
two diodes, back to back, which acts as the base terminal. 
 Statement II : In the study of transistor, the amplification factor ? indicates ratio of the 
collector current to the base current. 
 In the light of the above statements, choose the correct answer from the options given below. 
 (1) Statement I is false but Statement II is true. 
 (2) Both Statement I and Statement II are true 
 (3) Statement I is true but Statement II is false. 
 (4) Both Statement I and Statement II are false 
Ans. (1) 
Sol. S-1 
 Statement 1 is false because in case of two discrete back to back connected diodes, there are 
four doped regions instead of three and there is nothing that resembles a thin base region 
between an emitter and a collector. 
 S-2 
 Statement-2 is true, as 
 
C
B
I
I
? ? 
 
7. When a particle executes SHM, the nature of graphical representation of velocity as a function 
of displacement is : 
 (1)elliptical (2)parabolic (3)straight line  (4)circular 
Ans. (1) 
Sol. We know that is SHM; 
 
2 2
V A x ? ? ? 
 
V 
X 
 
 elliptical 
 
8. Match List – I with List – II. 
  List – I  List - II 
 (a) Source of microwave frequency (i) Radioactive decay of nucleus 
 (b) Source of infrared frequency (ii) Magnetron 
 (c) Source of Gamma Rays (iii) Inner shell electrons 
 (d) Source of X-rays (iv) Vibration of atoms and molecules 
    (v) LASER 
    (vi) RC circuit 
 Choose the correct answer from the options given below : 
 (1) (a)-(ii),(b)-(iv),(c)-(i),(d)-(iii) 
 (2) (a)-(vi),(b)-(iv),(c)-(i),(d)-(v) 
 (3) (a)-(ii),(b)-(iv),(c)-(vi),(d)-(iii) 
 (4) (a)-(vi),(b)-(v),(c)-(i),(d)-(iv) 
Ans. (1) 
Sol. (a) Source of microwave frequency – (ii) Magnetron 
 (b) Source of infra red frequency – (iv) Vibration of atom and molecules  
 (c) Source of gamma ray – (i) Radio active decay of nucleus 
 (d) Source of X-ray – (iii) inner shell electron 
 
Page 4


 
 
 
1. Zener breakdown occurs in a p-n junction having p and n both : 
 (1) lightly doped and have wide depletion layer. 
 (2) heavily doped andhave narrow depletion layer. 
 (3) heavily doped and have wide depletion layer. 
 (4) lightly doped and have narrow depletion layer. 
Ans. (2) 
Sol. The zener breakdown occurs in the heavily doped p-n junction diode. Heavily doped p-n 
junction diodes have narrow depletion region. 
 
2. According to Bohr atom model, in which of the following transitions will the frequency be 
maximum? 
 (1)n=2 to n=1 (2)n=4 to n =3 (3)n=5 to n=4 (4)n=3 to n=2 
Ans. (1) 
Sol. 
  
5 
4 
3 
2 
1 
?E=hf 
 
 f is more for transition from n = 2 to n = 1. 
 
3. An X-ray tube is operated at 1.24 million volt. The shortest wavelength of the produced photon 
will be : 
 (1) 10
-2
 nm (2)10
-3
 nm (3)10
-4
 nm (4)10
-1
 nm 
Ans. (2) 
Sol. 
min
hc
eV
? ? 
 
min
6
1240nm eV
1.24 10
?
? ?
?
 
 
3
min
10 nm
?
? ? 
 
4. On the basis of kinetic theory of gases, the gas exerts pressure because its molecules: 
 (1) suffer change in momentum when impinge on the walls of container. 
 (2) continuously stick to the walls of container. 
 (3) continuously lose their energy till it reaches wall. 
 (4) are attracted by the walls of container. 
Ans. (1) 
Sol. On the basis of kinetic theory of gases, the gas pressure is due to the molecules suffering 
change in momentum when impinge on the walls of container. 
 
24
th
 Feb. 2021 | Shift - 2
PHYSICS
 
 
5. A circular hole of radius 
a
2
? ?
? ?
? ?
 is cut out of a circular disc of radius ‘a’ shown in figure. The 
centroid of the remaining circular portion with respect to point ‘O’ will be : 
 
 
y-axis
O
a
a/2
x-axis
 
 
 (1)
10
a
11
 (2)
2
a
3
 (3)
1
a
6
 (4)
5
a
6
 
 
Ans. (4) 
 
Sol. Let ? is the surface mass density of disc. 
  
y 
x 
a/2 
a
3
2
 
y 
x 
a 
 
 
2
2
com
2
2
a 3a
( a a) ( )
4 2
X
a
a
4
?
? ? ? ? ? ? ?
?
? ?
? ? ?
 
 
com
a
a 3
8
X
1
1
4
?
?
?
 
 
com
5a
8
X
3
4
?
 
 
com
5a
X
6
? 
 
 
 
 
 
 
6. Given below are two statements : 
 Statement I : PN junction diodes can be used to function as transistor, simply by connecting 
two diodes, back to back, which acts as the base terminal. 
 Statement II : In the study of transistor, the amplification factor ? indicates ratio of the 
collector current to the base current. 
 In the light of the above statements, choose the correct answer from the options given below. 
 (1) Statement I is false but Statement II is true. 
 (2) Both Statement I and Statement II are true 
 (3) Statement I is true but Statement II is false. 
 (4) Both Statement I and Statement II are false 
Ans. (1) 
Sol. S-1 
 Statement 1 is false because in case of two discrete back to back connected diodes, there are 
four doped regions instead of three and there is nothing that resembles a thin base region 
between an emitter and a collector. 
 S-2 
 Statement-2 is true, as 
 
C
B
I
I
? ? 
 
7. When a particle executes SHM, the nature of graphical representation of velocity as a function 
of displacement is : 
 (1)elliptical (2)parabolic (3)straight line  (4)circular 
Ans. (1) 
Sol. We know that is SHM; 
 
2 2
V A x ? ? ? 
 
V 
X 
 
 elliptical 
 
8. Match List – I with List – II. 
  List – I  List - II 
 (a) Source of microwave frequency (i) Radioactive decay of nucleus 
 (b) Source of infrared frequency (ii) Magnetron 
 (c) Source of Gamma Rays (iii) Inner shell electrons 
 (d) Source of X-rays (iv) Vibration of atoms and molecules 
    (v) LASER 
    (vi) RC circuit 
 Choose the correct answer from the options given below : 
 (1) (a)-(ii),(b)-(iv),(c)-(i),(d)-(iii) 
 (2) (a)-(vi),(b)-(iv),(c)-(i),(d)-(v) 
 (3) (a)-(ii),(b)-(iv),(c)-(vi),(d)-(iii) 
 (4) (a)-(vi),(b)-(v),(c)-(i),(d)-(iv) 
Ans. (1) 
Sol. (a) Source of microwave frequency – (ii) Magnetron 
 (b) Source of infra red frequency – (iv) Vibration of atom and molecules  
 (c) Source of gamma ray – (i) Radio active decay of nucleus 
 (d) Source of X-ray – (iii) inner shell electron 
 
 
 
9. 
 
A
 
B
 
C
 
 
 The logic circuit shown above is equivalent to : 
 (1)
 
A
 
B
 
C 
 
 
(2)
 
A
 
B
 
C 
 
 
 (3)
 
A
 
B
 
C 
 
 
(4)
 
A
 
B
 
C
 
 
Ans. (2) 
Sol.  
A
 
B 
 
C 
 
 
 C A B ? ? 
 C A.B ?
 
 
10. If the source of light used in a Young’s double slit experiment is changed from red to violet: 
 (1)the fringes will become brighter. 
 (2)consecutive fringe lineswill come closer. 
 (3)the central bright fringe will become a dark fringe. 
 (4)the intensity of minima will increase. 
Ans. (2) 
Sol. 
D
d
?
? ? 
 As 
v R
? ? ? 
 
v R
? ? ? ? 
 ? ?Consecutive fringe line will come closer. 
 ? ?(2) 
 
11. A body weighs 49 N on a spring balance at the north pole. What will be its weight recorded on 
the same weighing machine, if it is shifted to the equator? 
 [Use g=
2
GM
R
 = 9.8 ms
-2
 and radius of earth, R = 6400 km.] 
 (1)49 N (2) 49.83 N (3) 49.17 N (4) 48.83 N 
Ans. (4) 
Sol. At north pole, weight 
 Mg = 49 
 Now, at equator 
 g’ = g- ?
2
R 
 
2
Mg' M(g R) ? ? ? ? 
 ? weight will be less than Mg at equator. 
 
Page 5


 
 
 
1. Zener breakdown occurs in a p-n junction having p and n both : 
 (1) lightly doped and have wide depletion layer. 
 (2) heavily doped andhave narrow depletion layer. 
 (3) heavily doped and have wide depletion layer. 
 (4) lightly doped and have narrow depletion layer. 
Ans. (2) 
Sol. The zener breakdown occurs in the heavily doped p-n junction diode. Heavily doped p-n 
junction diodes have narrow depletion region. 
 
2. According to Bohr atom model, in which of the following transitions will the frequency be 
maximum? 
 (1)n=2 to n=1 (2)n=4 to n =3 (3)n=5 to n=4 (4)n=3 to n=2 
Ans. (1) 
Sol. 
  
5 
4 
3 
2 
1 
?E=hf 
 
 f is more for transition from n = 2 to n = 1. 
 
3. An X-ray tube is operated at 1.24 million volt. The shortest wavelength of the produced photon 
will be : 
 (1) 10
-2
 nm (2)10
-3
 nm (3)10
-4
 nm (4)10
-1
 nm 
Ans. (2) 
Sol. 
min
hc
eV
? ? 
 
min
6
1240nm eV
1.24 10
?
? ?
?
 
 
3
min
10 nm
?
? ? 
 
4. On the basis of kinetic theory of gases, the gas exerts pressure because its molecules: 
 (1) suffer change in momentum when impinge on the walls of container. 
 (2) continuously stick to the walls of container. 
 (3) continuously lose their energy till it reaches wall. 
 (4) are attracted by the walls of container. 
Ans. (1) 
Sol. On the basis of kinetic theory of gases, the gas pressure is due to the molecules suffering 
change in momentum when impinge on the walls of container. 
 
24
th
 Feb. 2021 | Shift - 2
PHYSICS
 
 
5. A circular hole of radius 
a
2
? ?
? ?
? ?
 is cut out of a circular disc of radius ‘a’ shown in figure. The 
centroid of the remaining circular portion with respect to point ‘O’ will be : 
 
 
y-axis
O
a
a/2
x-axis
 
 
 (1)
10
a
11
 (2)
2
a
3
 (3)
1
a
6
 (4)
5
a
6
 
 
Ans. (4) 
 
Sol. Let ? is the surface mass density of disc. 
  
y 
x 
a/2 
a
3
2
 
y 
x 
a 
 
 
2
2
com
2
2
a 3a
( a a) ( )
4 2
X
a
a
4
?
? ? ? ? ? ? ?
?
? ?
? ? ?
 
 
com
a
a 3
8
X
1
1
4
?
?
?
 
 
com
5a
8
X
3
4
?
 
 
com
5a
X
6
? 
 
 
 
 
 
 
6. Given below are two statements : 
 Statement I : PN junction diodes can be used to function as transistor, simply by connecting 
two diodes, back to back, which acts as the base terminal. 
 Statement II : In the study of transistor, the amplification factor ? indicates ratio of the 
collector current to the base current. 
 In the light of the above statements, choose the correct answer from the options given below. 
 (1) Statement I is false but Statement II is true. 
 (2) Both Statement I and Statement II are true 
 (3) Statement I is true but Statement II is false. 
 (4) Both Statement I and Statement II are false 
Ans. (1) 
Sol. S-1 
 Statement 1 is false because in case of two discrete back to back connected diodes, there are 
four doped regions instead of three and there is nothing that resembles a thin base region 
between an emitter and a collector. 
 S-2 
 Statement-2 is true, as 
 
C
B
I
I
? ? 
 
7. When a particle executes SHM, the nature of graphical representation of velocity as a function 
of displacement is : 
 (1)elliptical (2)parabolic (3)straight line  (4)circular 
Ans. (1) 
Sol. We know that is SHM; 
 
2 2
V A x ? ? ? 
 
V 
X 
 
 elliptical 
 
8. Match List – I with List – II. 
  List – I  List - II 
 (a) Source of microwave frequency (i) Radioactive decay of nucleus 
 (b) Source of infrared frequency (ii) Magnetron 
 (c) Source of Gamma Rays (iii) Inner shell electrons 
 (d) Source of X-rays (iv) Vibration of atoms and molecules 
    (v) LASER 
    (vi) RC circuit 
 Choose the correct answer from the options given below : 
 (1) (a)-(ii),(b)-(iv),(c)-(i),(d)-(iii) 
 (2) (a)-(vi),(b)-(iv),(c)-(i),(d)-(v) 
 (3) (a)-(ii),(b)-(iv),(c)-(vi),(d)-(iii) 
 (4) (a)-(vi),(b)-(v),(c)-(i),(d)-(iv) 
Ans. (1) 
Sol. (a) Source of microwave frequency – (ii) Magnetron 
 (b) Source of infra red frequency – (iv) Vibration of atom and molecules  
 (c) Source of gamma ray – (i) Radio active decay of nucleus 
 (d) Source of X-ray – (iii) inner shell electron 
 
 
 
9. 
 
A
 
B
 
C
 
 
 The logic circuit shown above is equivalent to : 
 (1)
 
A
 
B
 
C 
 
 
(2)
 
A
 
B
 
C 
 
 
 (3)
 
A
 
B
 
C 
 
 
(4)
 
A
 
B
 
C
 
 
Ans. (2) 
Sol.  
A
 
B 
 
C 
 
 
 C A B ? ? 
 C A.B ?
 
 
10. If the source of light used in a Young’s double slit experiment is changed from red to violet: 
 (1)the fringes will become brighter. 
 (2)consecutive fringe lineswill come closer. 
 (3)the central bright fringe will become a dark fringe. 
 (4)the intensity of minima will increase. 
Ans. (2) 
Sol. 
D
d
?
? ? 
 As 
v R
? ? ? 
 
v R
? ? ? ? 
 ? ?Consecutive fringe line will come closer. 
 ? ?(2) 
 
11. A body weighs 49 N on a spring balance at the north pole. What will be its weight recorded on 
the same weighing machine, if it is shifted to the equator? 
 [Use g=
2
GM
R
 = 9.8 ms
-2
 and radius of earth, R = 6400 km.] 
 (1)49 N (2) 49.83 N (3) 49.17 N (4) 48.83 N 
Ans. (4) 
Sol. At north pole, weight 
 Mg = 49 
 Now, at equator 
 g’ = g- ?
2
R 
 
2
Mg' M(g R) ? ? ? ? 
 ? weight will be less than Mg at equator. 
 
 
 
12. If one mole of an ideal gas at (P
1
, V
1
) is allowed to expand reversibly and isothermally (A to B) 
its pressure is reduced to one-half of the original pressure (see figure). This is followed by a 
constant volume cooling till its pressure is reduced to one-fourth of the initial value (B ?C). 
Then it is restored to its initial state by a reversible adiabatic compression (C to A). The net 
workdone by the gas is equal to : 
 
B 
A
P
1
P
1
/2
P
1
/4
V
1
2V
1
V
C 
P
 
 (1)0  (2)-
RT
2( 1) ? ?
 
(3)
1
RT ln2
2( 1)
? ?
?
? ?
? ?
? ?
 
(4)RT ln2 
Ans. (3) 
Sol. AB ? Isothermal process 
 W
AB
? ?nRT ln2 = RT ln2 
 BC ? Isochoric process 
 W
BC
 = 0 
 CA ? ?Adiabatic process 
 
1
1 1 1
1 1
CA
P
P V X2V
P V RT
4
W
1 2(1 ) 2(1 )
?
? ? ?
? ? ? ? ? ?
 
 
ABCA
RT
W RT n2
2(1 )
? ?
? ?
? 
 
1
RT n2
2( 1)
? ?
? ?
? ?
? ?
? ?
? 
  
13. The period of oscillation of a simple pendulum is 
L
T 2
g
? ? . Measured value of ‘L’ is 1.0 m from meter 
scale having a minimum division of 1 mm and time of one complete oscillation is 1.95 s measured 
from stopwatch of 0.01 s resolution. The percentage error in the determination of ‘g’ will be : 
 (1)1.33 % (2)1.30 % (3)1.13 % (4)1.03 % 
Ans. (3) 
Sol. T 2
g
? ?
?
 
 
2 2
T 4
g
? ?
? ?
? ?
? ?
?
 
 
2
2
g 4
T
? ?
? ?
? ?
? ?
?
 
 
g 2 T
g T
? ? ?
? ?
?
?
 
 
3
1mm 2(10 10 )
100
1m 1.95
?
? ?
?
? ? ?
? ?
? ?
? ?
 
 = 1.13 %