PHYSICS
CAPACITANCE
JEE(ADVANCED)
TOPIC : CAPACITNCE DPP -14
1. An electron enters the region between the plates of a parallel plate capacitor at a point
equidistant from either plate. The capacitor plates are 2 x 102 m apart and 101 m long. A
potential difference of 300 volt is kept across the plates. Assuming that the initial velocity of the
electron is parallel to the capacitor plates, calculate the largest value of the velocity of the
electron so that they do not fly out of the capacitor at the other end. (take mass of electron = 9
× 10–31 kg)
(Comment By Resonance : 2 x 102 m apart and 101 m long, these data not for practical
capacitor).
2. Two capacitors A and B with capacitors 3µF and 2µF are charged to a potential difference of 100 V
and 180 V respectively. The plates of the capacitors are connected as shown in fig. with one wire
from each capacitor free. The upper plate of A is positive and that of B is negative. An uncharged
2µF capacitor C with lead wires falls on the free ends to complete the circuit. Calculate.
(i) The final charge on the three capacitors and
(ii) The amount of electrostatic energy stored in the system before and after the completion
of the circuit.
3. A dielectric slab of thickness d is inserted in a parallel plate capacitor whose negative plate
is at x = 0 and positive plate is at x = 3d. The slab is equidistant from the plates. The capacitor is
giv en some charge. As x goes from 0 to 3d.
(A) The magnitude of the electric field remains the same
(B) The direction of the electric field remains the same
(C) The electric potential increases continuously
(D) The electric potential increases at first, then decreases and again increases.
4. For the circuit shown, which of the following statements is true?
(A) With S1 closed, V1 = 15 V, V2 = 20 V
(B) With S3 closed, V1 = V2 = 25 V
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, (C) With S1 and S2 closed, V1 = V2 = 0
(D) With S1 and S2 closed, V1 = 30 V, V2 = 20 V
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,5. Consider the situation shown in the figure. The capacitor A has a charge q on it whereas B is
uncharged. The charge appearing on the capacitor B a long time after the switch is closed is
(A) zero (B) q/2 (C) q (D) 2 q
6. Two identical capacitors have the same capacitance C. One of them is charged to potential V1 and
the other to V2. The negative ends of the capacitors are connected together. When the positive ends
are also connected, the decrease in energy of the combined system is:
(A) 1 1
C (V 2
- V 2) (B) C (V 2
+ V 2)
1 2 1 2
4 4
1
1 C (V - V2)2 (D) C (V
(C) + V2)2
4 4
1 1
7. Dotted line represents the charging of a capacitor with resistance X. If resistance is made 2X then
which will be the graph of charging.
(A) P (B) Q (C) R (D) S
8. A parallel plate capacitor C with plates of unit area and separation d is filled with a liquid of dielectric
constant
d
K = 2. The level of liquid is initially. Suppose the liquid level decreases at a constant speed V, the
3
time
constant as a function of time t is
Figure :
C
d R
d
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, 6 0 R (15d 9V t) 0 R
(A) (B) 2d2 – 3d V t – 9V 2t2
5d 3V t
6 0 R (15 d – 9V t) 0 R
(C) (D)
5d– 3V t 2d2 3d V t – 9V 2t2
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CAPACITANCE
JEE(ADVANCED)
TOPIC : CAPACITNCE DPP -14
1. An electron enters the region between the plates of a parallel plate capacitor at a point
equidistant from either plate. The capacitor plates are 2 x 102 m apart and 101 m long. A
potential difference of 300 volt is kept across the plates. Assuming that the initial velocity of the
electron is parallel to the capacitor plates, calculate the largest value of the velocity of the
electron so that they do not fly out of the capacitor at the other end. (take mass of electron = 9
× 10–31 kg)
(Comment By Resonance : 2 x 102 m apart and 101 m long, these data not for practical
capacitor).
2. Two capacitors A and B with capacitors 3µF and 2µF are charged to a potential difference of 100 V
and 180 V respectively. The plates of the capacitors are connected as shown in fig. with one wire
from each capacitor free. The upper plate of A is positive and that of B is negative. An uncharged
2µF capacitor C with lead wires falls on the free ends to complete the circuit. Calculate.
(i) The final charge on the three capacitors and
(ii) The amount of electrostatic energy stored in the system before and after the completion
of the circuit.
3. A dielectric slab of thickness d is inserted in a parallel plate capacitor whose negative plate
is at x = 0 and positive plate is at x = 3d. The slab is equidistant from the plates. The capacitor is
giv en some charge. As x goes from 0 to 3d.
(A) The magnitude of the electric field remains the same
(B) The direction of the electric field remains the same
(C) The electric potential increases continuously
(D) The electric potential increases at first, then decreases and again increases.
4. For the circuit shown, which of the following statements is true?
(A) With S1 closed, V1 = 15 V, V2 = 20 V
(B) With S3 closed, V1 = V2 = 25 V
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, (C) With S1 and S2 closed, V1 = V2 = 0
(D) With S1 and S2 closed, V1 = 30 V, V2 = 20 V
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,5. Consider the situation shown in the figure. The capacitor A has a charge q on it whereas B is
uncharged. The charge appearing on the capacitor B a long time after the switch is closed is
(A) zero (B) q/2 (C) q (D) 2 q
6. Two identical capacitors have the same capacitance C. One of them is charged to potential V1 and
the other to V2. The negative ends of the capacitors are connected together. When the positive ends
are also connected, the decrease in energy of the combined system is:
(A) 1 1
C (V 2
- V 2) (B) C (V 2
+ V 2)
1 2 1 2
4 4
1
1 C (V - V2)2 (D) C (V
(C) + V2)2
4 4
1 1
7. Dotted line represents the charging of a capacitor with resistance X. If resistance is made 2X then
which will be the graph of charging.
(A) P (B) Q (C) R (D) S
8. A parallel plate capacitor C with plates of unit area and separation d is filled with a liquid of dielectric
constant
d
K = 2. The level of liquid is initially. Suppose the liquid level decreases at a constant speed V, the
3
time
constant as a function of time t is
Figure :
C
d R
d
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, 6 0 R (15d 9V t) 0 R
(A) (B) 2d2 – 3d V t – 9V 2t2
5d 3V t
6 0 R (15 d – 9V t) 0 R
(C) (D)
5d– 3V t 2d2 3d V t – 9V 2t2
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