JEE Main 2020 Physics September 4 Shift 1 Paper & Solutions | Mock Tests for JEE Main and Advanced 2025 PDF Download

 Page 1


JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 1
Date : 4th September 2020
Time : 09 : 00 am - 12 : 00 pm
Subject : Physics
Q.1 Starting from the origin at time t = 0, with initial velocity 
–1
ˆ
5jms , a particle moves in the
x-y plane with a constant acceleration of ? ?
–2
ˆ ˆ
10i 4j ms ?
. At time t, its coordinates are
(20 m, y
0
 m). The values of t and y
0 
are, respectively:
(1) 5s and 25 m (2) 2s and 18 m (3) 2s and 24 m (4) 4s and 52 m
Sol. 2
Equation of motion gives us
y = u
y
t + 
1
2
a
y
t
2
Here u
y
 = 5ms
–1
, u
x
 = 0 ms–1, a
x
 = 10ms
–2
, a
y
 = 4ms
–2
y = 5t + 
1
2
(4) t
2
y = 5t + 2t
2
and x = 0 + 
1
2
 (10) (t
2
) = 20
t = 2 s
? y = 10 + 8 = 18m
Q.2 A small bar magnet placed with its axis at 30° with an external field of 0.06 T experi-
ences a torque of 0.018 Nm. The minimum work required to rotate it from its stable to
unstable equilbrium position is:
(1) 7.2 × 10
–2
 J (2) 6.4 × 10
–2
 J (3) 9.2 × 10
–3
 J (4) 11.7 × 10
–3
 J
Sol. 1
? = MB sin 30º
0.018 = MB
1
2
? ?
? ?
? ?
MB = 0.036
w = ?U = |MB cos0
0 
—MB cos 180
0
| = 2MB = 0.072 J
Q.3 Choose the correct option relating wave lengths of different parts of electromagnetic
wave spectrum:
(1) ?
radio waves
 > ?
micro waves
 > ?
visible
 > ?
x-rays
(2) ?
visible 
> ?
x-rays 
> ?
radio waves 
> ?
micro waves
(3) ?
visible 
< ?
micro waves
 < ?
radio waves
 < ?
x-rays
(4) ?
x-rays
 < ?
micro waves
 < ?
radio waves
 < ?
visible
Sol. 1
By property of electromagnetic wave spectrum.
Page 2


JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 1
Date : 4th September 2020
Time : 09 : 00 am - 12 : 00 pm
Subject : Physics
Q.1 Starting from the origin at time t = 0, with initial velocity 
–1
ˆ
5jms , a particle moves in the
x-y plane with a constant acceleration of ? ?
–2
ˆ ˆ
10i 4j ms ?
. At time t, its coordinates are
(20 m, y
0
 m). The values of t and y
0 
are, respectively:
(1) 5s and 25 m (2) 2s and 18 m (3) 2s and 24 m (4) 4s and 52 m
Sol. 2
Equation of motion gives us
y = u
y
t + 
1
2
a
y
t
2
Here u
y
 = 5ms
–1
, u
x
 = 0 ms–1, a
x
 = 10ms
–2
, a
y
 = 4ms
–2
y = 5t + 
1
2
(4) t
2
y = 5t + 2t
2
and x = 0 + 
1
2
 (10) (t
2
) = 20
t = 2 s
? y = 10 + 8 = 18m
Q.2 A small bar magnet placed with its axis at 30° with an external field of 0.06 T experi-
ences a torque of 0.018 Nm. The minimum work required to rotate it from its stable to
unstable equilbrium position is:
(1) 7.2 × 10
–2
 J (2) 6.4 × 10
–2
 J (3) 9.2 × 10
–3
 J (4) 11.7 × 10
–3
 J
Sol. 1
? = MB sin 30º
0.018 = MB
1
2
? ?
? ?
? ?
MB = 0.036
w = ?U = |MB cos0
0 
—MB cos 180
0
| = 2MB = 0.072 J
Q.3 Choose the correct option relating wave lengths of different parts of electromagnetic
wave spectrum:
(1) ?
radio waves
 > ?
micro waves
 > ?
visible
 > ?
x-rays
(2) ?
visible 
> ?
x-rays 
> ?
radio waves 
> ?
micro waves
(3) ?
visible 
< ?
micro waves
 < ?
radio waves
 < ?
x-rays
(4) ?
x-rays
 < ?
micro waves
 < ?
radio waves
 < ?
visible
Sol. 1
By property of electromagnetic wave spectrum.
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 2
Q.4 On the x-axis and at a distance x from the origin, the gravitational field due a mass
distribution is given by 
? ?
3/2
2 2
Ax
x a ?
in the x-direction. The magnitude of gravitational
potential on the x-axis at a distance x, taking its value to be zero at infinity, is:
(1) 
? ?
3/2
2 2
A x a ? (2) 
? ?
1/2
2 2
A
x a ?
(3) 
? ?
1/2
2 2
A x a ? (4) 
? ?
3/2
2 2
A
x a ?
Sol. 2
E
x
 = 2 2 3/2
(x a )
Ax
?
2 2 3/2
–
(x a )
?
?
dV Ax
dx
2 2 3/2
0
–
(x a )
?
?
?
? ?
V x
Ax
dV dx
V = 2 2 1/2
(x )
A
a ?
Q.5 A small bar magnet is moved through a coil at constant speed from one end to the other.
Which of the following series of observations will be seen on the galvanometer G at-
tached across the coil?
Three positions shown describe: (a) the magnet's entry (b) magnet is completely inside
and (c) magnet's exit.
(1) 
(2) 
Page 3


JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 1
Date : 4th September 2020
Time : 09 : 00 am - 12 : 00 pm
Subject : Physics
Q.1 Starting from the origin at time t = 0, with initial velocity 
–1
ˆ
5jms , a particle moves in the
x-y plane with a constant acceleration of ? ?
–2
ˆ ˆ
10i 4j ms ?
. At time t, its coordinates are
(20 m, y
0
 m). The values of t and y
0 
are, respectively:
(1) 5s and 25 m (2) 2s and 18 m (3) 2s and 24 m (4) 4s and 52 m
Sol. 2
Equation of motion gives us
y = u
y
t + 
1
2
a
y
t
2
Here u
y
 = 5ms
–1
, u
x
 = 0 ms–1, a
x
 = 10ms
–2
, a
y
 = 4ms
–2
y = 5t + 
1
2
(4) t
2
y = 5t + 2t
2
and x = 0 + 
1
2
 (10) (t
2
) = 20
t = 2 s
? y = 10 + 8 = 18m
Q.2 A small bar magnet placed with its axis at 30° with an external field of 0.06 T experi-
ences a torque of 0.018 Nm. The minimum work required to rotate it from its stable to
unstable equilbrium position is:
(1) 7.2 × 10
–2
 J (2) 6.4 × 10
–2
 J (3) 9.2 × 10
–3
 J (4) 11.7 × 10
–3
 J
Sol. 1
? = MB sin 30º
0.018 = MB
1
2
? ?
? ?
? ?
MB = 0.036
w = ?U = |MB cos0
0 
—MB cos 180
0
| = 2MB = 0.072 J
Q.3 Choose the correct option relating wave lengths of different parts of electromagnetic
wave spectrum:
(1) ?
radio waves
 > ?
micro waves
 > ?
visible
 > ?
x-rays
(2) ?
visible 
> ?
x-rays 
> ?
radio waves 
> ?
micro waves
(3) ?
visible 
< ?
micro waves
 < ?
radio waves
 < ?
x-rays
(4) ?
x-rays
 < ?
micro waves
 < ?
radio waves
 < ?
visible
Sol. 1
By property of electromagnetic wave spectrum.
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 2
Q.4 On the x-axis and at a distance x from the origin, the gravitational field due a mass
distribution is given by 
? ?
3/2
2 2
Ax
x a ?
in the x-direction. The magnitude of gravitational
potential on the x-axis at a distance x, taking its value to be zero at infinity, is:
(1) 
? ?
3/2
2 2
A x a ? (2) 
? ?
1/2
2 2
A
x a ?
(3) 
? ?
1/2
2 2
A x a ? (4) 
? ?
3/2
2 2
A
x a ?
Sol. 2
E
x
 = 2 2 3/2
(x a )
Ax
?
2 2 3/2
–
(x a )
?
?
dV Ax
dx
2 2 3/2
0
–
(x a )
?
?
?
? ?
V x
Ax
dV dx
V = 2 2 1/2
(x )
A
a ?
Q.5 A small bar magnet is moved through a coil at constant speed from one end to the other.
Which of the following series of observations will be seen on the galvanometer G at-
tached across the coil?
Three positions shown describe: (a) the magnet's entry (b) magnet is completely inside
and (c) magnet's exit.
(1) 
(2) 
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 3
(3) 
(4) 
Sol. 1
Let N S
? When bar magnet enters the coil,  emf is generated due to magnetic flux change.
N
? When completely inside
i = 0
? when bar magnet exits the coil, emf is generated again but of opposite nature.
S
S
N
N
Q.6 A battery of 3.0V is connected to a resistor dissipating 0.5 W of power. If the terminal
voltage of the battery is 2.5V, the power dissipated within the internal resistance is:
(1) 0.072 W (2) 0.10 W (3) 0.125 W (4) 0.50 W
Sol. 2
P
0
 = 0.5 W
i. (2.5) = 0.5
r
R
i
i = 1/5 A
P
r
 = 
1
5
? ?
? ?
? ?
(0.5) = 0.1 W
Page 4


JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 1
Date : 4th September 2020
Time : 09 : 00 am - 12 : 00 pm
Subject : Physics
Q.1 Starting from the origin at time t = 0, with initial velocity 
–1
ˆ
5jms , a particle moves in the
x-y plane with a constant acceleration of ? ?
–2
ˆ ˆ
10i 4j ms ?
. At time t, its coordinates are
(20 m, y
0
 m). The values of t and y
0 
are, respectively:
(1) 5s and 25 m (2) 2s and 18 m (3) 2s and 24 m (4) 4s and 52 m
Sol. 2
Equation of motion gives us
y = u
y
t + 
1
2
a
y
t
2
Here u
y
 = 5ms
–1
, u
x
 = 0 ms–1, a
x
 = 10ms
–2
, a
y
 = 4ms
–2
y = 5t + 
1
2
(4) t
2
y = 5t + 2t
2
and x = 0 + 
1
2
 (10) (t
2
) = 20
t = 2 s
? y = 10 + 8 = 18m
Q.2 A small bar magnet placed with its axis at 30° with an external field of 0.06 T experi-
ences a torque of 0.018 Nm. The minimum work required to rotate it from its stable to
unstable equilbrium position is:
(1) 7.2 × 10
–2
 J (2) 6.4 × 10
–2
 J (3) 9.2 × 10
–3
 J (4) 11.7 × 10
–3
 J
Sol. 1
? = MB sin 30º
0.018 = MB
1
2
? ?
? ?
? ?
MB = 0.036
w = ?U = |MB cos0
0 
—MB cos 180
0
| = 2MB = 0.072 J
Q.3 Choose the correct option relating wave lengths of different parts of electromagnetic
wave spectrum:
(1) ?
radio waves
 > ?
micro waves
 > ?
visible
 > ?
x-rays
(2) ?
visible 
> ?
x-rays 
> ?
radio waves 
> ?
micro waves
(3) ?
visible 
< ?
micro waves
 < ?
radio waves
 < ?
x-rays
(4) ?
x-rays
 < ?
micro waves
 < ?
radio waves
 < ?
visible
Sol. 1
By property of electromagnetic wave spectrum.
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 2
Q.4 On the x-axis and at a distance x from the origin, the gravitational field due a mass
distribution is given by 
? ?
3/2
2 2
Ax
x a ?
in the x-direction. The magnitude of gravitational
potential on the x-axis at a distance x, taking its value to be zero at infinity, is:
(1) 
? ?
3/2
2 2
A x a ? (2) 
? ?
1/2
2 2
A
x a ?
(3) 
? ?
1/2
2 2
A x a ? (4) 
? ?
3/2
2 2
A
x a ?
Sol. 2
E
x
 = 2 2 3/2
(x a )
Ax
?
2 2 3/2
–
(x a )
?
?
dV Ax
dx
2 2 3/2
0
–
(x a )
?
?
?
? ?
V x
Ax
dV dx
V = 2 2 1/2
(x )
A
a ?
Q.5 A small bar magnet is moved through a coil at constant speed from one end to the other.
Which of the following series of observations will be seen on the galvanometer G at-
tached across the coil?
Three positions shown describe: (a) the magnet's entry (b) magnet is completely inside
and (c) magnet's exit.
(1) 
(2) 
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 3
(3) 
(4) 
Sol. 1
Let N S
? When bar magnet enters the coil,  emf is generated due to magnetic flux change.
N
? When completely inside
i = 0
? when bar magnet exits the coil, emf is generated again but of opposite nature.
S
S
N
N
Q.6 A battery of 3.0V is connected to a resistor dissipating 0.5 W of power. If the terminal
voltage of the battery is 2.5V, the power dissipated within the internal resistance is:
(1) 0.072 W (2) 0.10 W (3) 0.125 W (4) 0.50 W
Sol. 2
P
0
 = 0.5 W
i. (2.5) = 0.5
r
R
i
i = 1/5 A
P
r
 = 
1
5
? ?
? ?
? ?
(0.5) = 0.1 W
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 4
Q.7 Two charged thin infinite plane sheets of uniform surface charge density ?
+
 and ?
–
, where
| ?
+
| > | ?
–
|, intersect at right angle. Which of the following best represents the electric field
lines for this system:
(1) (2) 
(3) (4) 
Sol. 1
Let us choose points A,B,C,D as shown to understand the direction of net electric field
to get a better picture.
 +
 –
E E 
E 
E 
E
–
E
–
E
+
E
+
E
–
E
+
0
E
+
E
–
s +
A B
C D
– E E ? ?
? > 45°
Page 5


JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 1
Date : 4th September 2020
Time : 09 : 00 am - 12 : 00 pm
Subject : Physics
Q.1 Starting from the origin at time t = 0, with initial velocity 
–1
ˆ
5jms , a particle moves in the
x-y plane with a constant acceleration of ? ?
–2
ˆ ˆ
10i 4j ms ?
. At time t, its coordinates are
(20 m, y
0
 m). The values of t and y
0 
are, respectively:
(1) 5s and 25 m (2) 2s and 18 m (3) 2s and 24 m (4) 4s and 52 m
Sol. 2
Equation of motion gives us
y = u
y
t + 
1
2
a
y
t
2
Here u
y
 = 5ms
–1
, u
x
 = 0 ms–1, a
x
 = 10ms
–2
, a
y
 = 4ms
–2
y = 5t + 
1
2
(4) t
2
y = 5t + 2t
2
and x = 0 + 
1
2
 (10) (t
2
) = 20
t = 2 s
? y = 10 + 8 = 18m
Q.2 A small bar magnet placed with its axis at 30° with an external field of 0.06 T experi-
ences a torque of 0.018 Nm. The minimum work required to rotate it from its stable to
unstable equilbrium position is:
(1) 7.2 × 10
–2
 J (2) 6.4 × 10
–2
 J (3) 9.2 × 10
–3
 J (4) 11.7 × 10
–3
 J
Sol. 1
? = MB sin 30º
0.018 = MB
1
2
? ?
? ?
? ?
MB = 0.036
w = ?U = |MB cos0
0 
—MB cos 180
0
| = 2MB = 0.072 J
Q.3 Choose the correct option relating wave lengths of different parts of electromagnetic
wave spectrum:
(1) ?
radio waves
 > ?
micro waves
 > ?
visible
 > ?
x-rays
(2) ?
visible 
> ?
x-rays 
> ?
radio waves 
> ?
micro waves
(3) ?
visible 
< ?
micro waves
 < ?
radio waves
 < ?
x-rays
(4) ?
x-rays
 < ?
micro waves
 < ?
radio waves
 < ?
visible
Sol. 1
By property of electromagnetic wave spectrum.
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 2
Q.4 On the x-axis and at a distance x from the origin, the gravitational field due a mass
distribution is given by 
? ?
3/2
2 2
Ax
x a ?
in the x-direction. The magnitude of gravitational
potential on the x-axis at a distance x, taking its value to be zero at infinity, is:
(1) 
? ?
3/2
2 2
A x a ? (2) 
? ?
1/2
2 2
A
x a ?
(3) 
? ?
1/2
2 2
A x a ? (4) 
? ?
3/2
2 2
A
x a ?
Sol. 2
E
x
 = 2 2 3/2
(x a )
Ax
?
2 2 3/2
–
(x a )
?
?
dV Ax
dx
2 2 3/2
0
–
(x a )
?
?
?
? ?
V x
Ax
dV dx
V = 2 2 1/2
(x )
A
a ?
Q.5 A small bar magnet is moved through a coil at constant speed from one end to the other.
Which of the following series of observations will be seen on the galvanometer G at-
tached across the coil?
Three positions shown describe: (a) the magnet's entry (b) magnet is completely inside
and (c) magnet's exit.
(1) 
(2) 
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 3
(3) 
(4) 
Sol. 1
Let N S
? When bar magnet enters the coil,  emf is generated due to magnetic flux change.
N
? When completely inside
i = 0
? when bar magnet exits the coil, emf is generated again but of opposite nature.
S
S
N
N
Q.6 A battery of 3.0V is connected to a resistor dissipating 0.5 W of power. If the terminal
voltage of the battery is 2.5V, the power dissipated within the internal resistance is:
(1) 0.072 W (2) 0.10 W (3) 0.125 W (4) 0.50 W
Sol. 2
P
0
 = 0.5 W
i. (2.5) = 0.5
r
R
i
i = 1/5 A
P
r
 = 
1
5
? ?
? ?
? ?
(0.5) = 0.1 W
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 4
Q.7 Two charged thin infinite plane sheets of uniform surface charge density ?
+
 and ?
–
, where
| ?
+
| > | ?
–
|, intersect at right angle. Which of the following best represents the electric field
lines for this system:
(1) (2) 
(3) (4) 
Sol. 1
Let us choose points A,B,C,D as shown to understand the direction of net electric field
to get a better picture.
 +
 –
E E 
E 
E 
E
–
E
–
E
+
E
+
E
–
E
+
0
E
+
E
–
s +
A B
C D
– E E ? ?
? > 45°
JEE Main 2020 Paper
         4
th
 September 2020 | (Shift-1), Physics     Page | 5
Q.8 An air bubble of radius 1 cm in water has an upward acceleration 9.8 cm s
–2
. The density
of water is 1 gm cm
–3
 and water offers negligible drag force on the bubble. The mass of
the bubble is (g = 980 cm/s
2
).
(1) 1.52 gm (2) 4.51 gm (3) 3.15 gm (4) 4.15 gm
Sol. 4
F
b
mg
F
b
 –mg = ma ? 
b
F
m
g a
?
?
w
V g
m
g a
? ?
?
?
m =  
3
(4 / 3) r . .
?
w
g
g a
? ?
= 4.15 gram
Q.9 A wire A, bent in the shape of an arc of a circle, carrying a current of 2A and having
radius 2 cm and another wire B, also bent in the shape of arc of a circle, carrying a
current of 3 A and having radius of 4 cm, are placed as shown in the figure. The ratio of
the magnetic field due to the wires A and B at the common centre O is:
90°
60°
B
O
A
(1) 2 : 5 (2) 6 : 5 (3) 6 : 4 (4) 4 : 6
Sol. 2
A
3
(2)
2 3
B
2(a)(2 ) 4a
? ? ?
?
? ?
?
? ?
? ?
?
B
5
(3)
3 5
B
2(2a)(2 ) 8a
? ? ?
?
? ?
?
? ?
? ?
?
A
B
B 3 8a
6:5
B 4a 5
?
? ? ?
?