PHYSICS

Target : NEET 2020

Rapid Revision Course

CAPACITOR

Contents
Topic Page No.

Exercise-1 2-8

Exercise-2 9 - 10

Answer Key 11

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 2 Physics for NEET
8. The value of one farad in e.s.u. is-
EXERCISE-1 (A) 3 × 10
10
(B) 9 × 10
11

DEFINITION OF CAPACITANCE 1 –11 1 –10

(C) × 10 (D) × 10
9 3
1. The radii of two metallic spheres are 5 cm and 10 cm and
both carry equal charge of 75C. If the two spheres are 9. A parallel plate air capacitor is charged to a potential
shorted then charge will be transferred difference V. After disconnecting the battery the
(A) 25 C from smaller to bigger distance between the plates of the capacitor is
(B) 25 C from bigger to smaller increased using an insulating handle. As a result the
(C) 50 C from smaller to bigger potential difference between the plates-
(D) 50 C from bigger to smaller (A) Increases (B) Decreases
(C) Does not change (D) Becomes zero
2. Two isolated charged metallic spheres of radii R1 and
R2 having charges Q1 and Q2 respectively are connected 10. In a charged capacitor the energy is stored in-
to each other, then there is: (A) The edges of the capacitor plates
(A) No change in the electrical energy of the system (B) The electric field between the plates
(B) An increase in the electrical energy of the system (C) Both in positive and negative charges
(C) Always a decrease in the electrical energy of the (D) Positive charges
system 11. The capacity of a parallel plate capacitor depends
(D) A decrease in electrical energy of the system until upon-
Q1 R2 = Q2 R1 (A) Nature of the metal
3. The air between the plates of a parallel plate capacitor (B) Distance between the plates
is replaced by a medium of dielectric constant K. The (C) Thickness of the plates
(D) Potential difference between the plates
capacitance becomes
12. The capacitance of a parallel plate capacitor is 10 µF
1 when distance between its plates is 8 cm. If distance
(A) K times (B) times
K between the plates is reduced to 4 cm, its capacitance
will be-
1 (A) 5 µF (B) 10 µF
(C) K times (D)
K
times
(C) 20 µF (D) 40 µF
13. Capacitance in farad of a spherical conductor with
4. A parallel plate capacitor is charged and then isolated. radius 1 metre is-
On increasing the plate separation– (A) 1.1 × 10
–10
(B) 10
–6
Charge Potential Capacitance (C) 9 × 10
–9
(D) 10
–3
(A) remains constant remains constant decreases
(B)remains constant increases decreases 14. The capacitance of spherical conductor is given by-
(C) remains constant decreases increases 1
(A) C  (B) C = 40 R
(D)increases increases decreases 40 R
2 3
5. If we increase the distance between two plates of the (C) C = 40 R (D) C = r0 R
capacitor, the capacitance will 15. Capacity of a conductor depends upon-
(A) decrease (A) Size of conductor
(B) remain same (B) Thickness of conductor
(C) increase (C) Material of conductor
(D) first decrease then increase (D) All of these
CIRCUITS WITH CAPACITOR AND USE OF KCL
6. The capacity of a parallel plate capacitor increases AND KVL
with the-
(A) Decrease of its area 16. The work done against electric forces in increasing the
(B) Increase of its distance potential difference of a condenser from 20V to 40V is
(C) Increase of its area W. The work done in increasing its potential difference
(D) None of the above from 40V to 50V will be
3W W
7. The capacity of an isolated conducting sphere of (A) 4W (B) (C) 2W (D)
radius R is proportional to- 4 2
1 1 17. The magnitude of charge in steady state on either of
2
(A) R (B) 2 (C) (D) R the plates of condenser C in the adjoining circuit is-
R R
 CAPACITOR 3

1 V2 1 V2
(A) 0 (B)
2 d2 2 0 d 2
1 2 Q2
(C) CV (D)
2 2C
CER 2 25. The mean electric energy density between plates of
(A) CE (B) (R  r) a charged capacitor is- (here q = charge on the
1
capacitor and A = area of the capacitor plate)
CER 2 CER1
(C) (R  r) (D) (R  r) q2 q
2 2 (A) (B)
2 0 A 2 2 0 A 2
18. The plate separation in a parallel plate condenser is d
and plate area is A. If it is charged to V volt & battery is q2
disconnected then the work done in increasing the plate (C) (D) None of above
2 0 A
separation to 2d will be– 26. A capacitor when charged by a potential difference
2
3  0 AV  0 AV 2 of 200 volt, stores a charge of 0.1 C. By discharging,
(A) (B) energy liberated by the capacitor is-
2 d d
(A) –30 J (B) –15 J
2 0 AV 2  0 AV 2 (C) 10 J (D) 20 J
(C) (D)
d 2d 27. A capacitor of capacity C is charged upto V volt and
19. A capacitor of capacitance C1 is charged to potential then connected to an uncharged capacitor of capacity
C2. Then final potential difference across each will be-
V and battery is disconnected. Now the capacitor is
connected to a uncharged capacitor of capacitance C2 C2V  C2 
then what will be common potential of the combination (A) (B) 1  V
C1  C 2  C1 
C1V C2 V
(A) C  C (B) C  C C1V  C2 
1 2 1 2 (C) (D) 1  V
C1  C 2  C1 
 C1  C2  V C2
(C) (D) C  C –18
C1  C2 1 2 28. Work done in placing a charge of 8 × 10 C
20. If the charge on a body is increased by 2C, the on a condenser of capacity 100 microfarad is-
–32 –26
energy stored in it increases by 21%. The original (A) 16 × 10 J (B) 3.1 × 10 J
–10 –32
charge on the body in micro-coulombs is (C) 4 × 10 J (D) 32 × 10 J
(A) 10 (B) 20 (C) 30 (D) 40 29. The work done in doubling the separation between
21. What fraction of the energy drawn from the charging plates of a parallel plate capacitor of capacity C and
battery is stored in a capacitor having charge Q is-
(A) 100% (B) 75% (C) 50% (D) 25% Q2 Q2 Q2 2Q 2
(A) (B) (C) (D)
22. The plates of a parallel plate condenser are pulled apart C 2C 4C C
with a velocity v. If at any instant mutual distance of 30. A capacitor is charged by connecting a battery across
separation is d, then the magnitude of the time of rate its plates. It stores energy U. Now the battery is
of change of electrostatic energy of the capacity disconnected and another identical capacitor is
depends on d as follows- connected across it, then the energy stored by both
1 1 capacitors of the system will be :
2
(A) (B) (C) d (D) d U 3
d d2 (A) U (B) (C) 2U (D) U
23. 125 water drops of equal radius and equal capacitance 2 2
C, coalesce to form a single drop of capacitance C´. 31. In a parallel plate capacitor, the distance between the
The relation between C and C´ is- plates is d and potential difference across plates is V.
(A) C´ = 125 C (B) C´ = C Energy stored per unit volume between the plates of
C capacitor is :
(C) C´ (D) C´ = 5C
125 Q2 1 V2
(A) (B) 0
24. Energy per unit volume for a capacitor having area A 2V 2 2 d2
and separation d kept at potential difference V is given 02 V 2 1  20 V 2
by (C) (D)
d2 2 d2
 4 Physics for NEET
COMBINATION OF CAPACITORS
32. In the adjoining circuit, the capacity between the points
A and B will be -

(A) 40F (B) 20F (C) 30F (D) 10F

37. Two capacitors of 1F and 2F are connected in series,
(A) C (B) 2C (C) 3C (D) 4C the resultant capacitance will be
33. The resultant capacity between the points A and B in 2 3
(A) 4F (B) F (C) F (D) 3F
the adjoining circuit will be - 3 2
38. Equivalent capacity between A and B is :

(A) 2 F (B) 3 F
(C) 4 F (D) 0.5 F
39. Two capacitors of capacity C1 and C2 are charged upto
a potential V1 and V2 , then condition for not flowing
the charge between on connected them in parallel.
(A) C (B) 2C (C) 3C (D) 4C (A) C1 = C2 (B) C1V1 = C2V2
34. The effective capacity in the following figure between C1 2 C
the points P and Q will be – (C) V1 = V2 (D) V  V
1 2

40. Three capacitors of capacity 1 F each, are connected

in such a way, that resultant capacity is 1.5 F, then:
(A) all the capacitors are joned in series
(B) all the capacitors are joined in parallel
(C) two capacitors are in parallel, while third is in series
(A) 3F (B) 5F (C) 2F (D) 1F (D) two capacitors are in series, while third is in parallel
35. The charge on the condenser of capacitance 2F in the 41. n identical condenser are joined in parallel and
following circuit will be – are charged to potential V. Now they are separated
and joined in series. Then the total energy and
potential difference of the combination will be-
(A) Energy and potential difference remain same
(B) Energy remains same and potential difference is
nV
(C) Energy increases n times and potentials
differences is nV
(D) Energy increases n times and potential difference
remains same
(A) 4.5 C (B) 6.0 C (C) 7 C (D) 30 C 42. Three different capacitors are connected in series.
36. Five capacitors of 10F capacity each are connected Then-
to a d.c. potential difference of 100 volts as shown (A) They will have equal charges
in the figure. The equivalent capacitance between the (B) They will have same potential
points A and B will be equal to- (C) Both 1 and 2
(D) None of these
 CAPACITOR 5
43. The equivalent capacitance of three capacitors of 52. Conducting sphere of radius R 1 is covered by
capacitance C1, C2 and C3 connected in parallel is 12 concentric sphere of radius R2. Capacity of this
units and the product C1 . C2 . C3 = 48. When the combination is proportional to-
capacitors C1 and C2 are connected in parallel the R 2  R1 R 2  R1
equivalent capacitance is 6 units. Then the (A) (B)
R1 R 2 R1 R 2
capacitance are-
(A) 2, 4, 6 (B) 1, 5, 6 R1 R 2 R1 R 2
(C) (D)
(C) 1.5, 2.5, 8 (D) 2, 3, 7 R1  R 2 R 2  R1
44. Ten capacitors are joined in parallel and charged with 53. A capacitor of 10µF charged up to 250 volts is
a battery up to a potential V. They are then disconnected connected in parallel with another capacitor of 5µF
from battery and joined again in series then the potential charged up to 100 volts. The common potential is-
of this combination will be- (A) 500 V (B) 60 V
(A) V (B) 10 V (C) 5 V (D) 2 V (C) 300 V (D) 200 V
45. The energy stored in the capacitor is U, when it is 54. Two capacitors when connected in series have a
charged with a battery. After disconnecting battery capacitance of 3 µF, and when connected in parallel
another capacitor of same capacity is connected in have a capacitance of 16 µF. Their individual capacities
are-
parallel with it, then energy stored in each capacitor
(A) 1 µF, 2 µF (B) 6 µF, 2 µF
is
(C) 12 µF, 4 µF (D) 3 µF, 16 µF
U U 55. Three capacitors each of capacity 4 µF are to be
(A) (B) (C) 9U (D) 8U
6 4 connected in such a way that the effective capacitance
46. Two capacitors with capacitances C 1 and C2 are is 6 µF. This can be done by connecting-
charged to potentials V1 and V2 respectively. When (A) All of them in series
they are connected in parallel the ratio of their (B) All of them in parallel
respective charges is- (C) Two in parallel and one is series
C12 (D) Two in series and one in parallel
V2 C1 V1
(A) (B) (C) (D) 56. A parallel plate capacitor is formed by placing
V22 C 22 C2 V2
n plates in alternate series one over another.
47. Minimum numbers of 8µF and 250V capacitors are If the capacity between any two consecutive
used to make a combination of 16µF and 1000V plates is C, then total capacity of the capacitor
are- is-
(A) 4 (B) 32 (C) 8 (D) 3 (A) C (B) nC
(C) (n – 1) C (D) (n + 1) C
48. A potential difference of 300 volts is applied to a
combination of 2µF and 8µF capacitors connected in 57. A series combination of three capacitors of
series. The charge on the 2µF capacitor is- capacitances 1µF, 2µF and 8µF is connected in series
–4 –4
(A) 2.4 × 10 coulomb (B) 4.8 × 10 coulomb to a battery of emf 13 volt. The potential difference
–4 –4
(C) 7.2 × 10 coulomb (D) 9.6 × 10 coulomb across the plates of 2µF capacitor will be-
49. A condenser of capacity 50 µF is charged to 10V. The 13
energy stored is- (A) 1 V (B) 8 V (C) V (D) V
–3 –3 3
(A) 1.25 × 10 J (B) 2.5 × 10 J
–3 –3 58. Consider the situation shown in fig. The capacitor A
(C) 3.75 × 10 J (D) 5 × 10 J
has a charge q on it whereas B is uncharged. The
50. Three condenser of capacity C each are joined first
charge appearing on the capacitor B a long time after
in series and then in parallel. The capacity becomes
the switch is closed is-
n times, where n is-
q
(A) 3 (B) 6 (C) 9 (D) 12
+
51. Two spherical conductors A and B of radius a and
b (b > a) are placed in air concentrically. B is given +
charge +Q coulomb and A is grounded. The +
equivalent capacitance of these will be- s
ab +
(A) 4  0 (B) 40 (a + b) +
ba A B
2
b q
(C) 40b (D) 4  0 (A) Zero (B) (C) q (D) 2q
ba 2
 6 Physics for NEET
59. The outer sphere of a spherical air capacitor (i) the current in the circuit is :
is earthed. For increasing its capacitance- (A) 4.42 A (B) 6 A
(A) Vaccum is created between two sphere (C) 2.21 A (D) 0 A
(B) Dielectric material is filled between the two spheres
(C) The space between two spheres is increased (ii) the power spent by the battery is :
(D) The earthing of the outer sphere is removed (A) 26.4 W (B) 13.2 W
(C) 4.87 W (D) 0
60. Two capacitors are joined as shown in figure.
Potentials at points A and B are V1 and V2 respectively. (iii) the power dissipated in heat is :
The potential of point D is - (A) 26.4 W (B) 13.2 W
D B (C) 4.87 W (D) 0
A
V1 C1 C2 V2 (iv) the rate at which energy stored in the capacitor is
increasing is :
1 C1V2  C 2 V1 (A) 26.4 W (B) 13.2 W
(A) (V1  V2 ) (B)
2 C1  C 2 (C) 4.87 W (D) 8.37 W
64. The charge on each of the capacitors 0.20 ms after the
C1V1  C2 V2 C 2 V1  C1V2
(C) (D) switch S is closed in figure is :
C1  C 2 C1  C2

EQUATION OF CHARGING AND

DISCHARGING
61. The plates of a capacitor of capacitance 10 F, charged
to 60 C, are joined together by a wire of resistance 10
 at t = 0, then
(i) the charge on the capacitor in the circuit at t = 0 is : (A) 24 C (B) 16.8 C
(A) 120 C (B) 60 C (C) 10.37 C (D) 4.5 C
(C) 30 C (D) 44 C 65. Time constant of a series R-C circuit is
(ii) the charge on the capacitor in the circuit at t = 100 s (A) +RC (B) –RC
is : (C) R/C (D) C/R
(A) 120 C (B) 60 C 66. If a current, that charges a capacitor, is constant, then
(C) 22 C (D) 18 C graph representing the change in voltage across the
(iii) the charge on the capacitor in the circuit at t = 1.0 ms capacitor with time t is-
is :
(A) 0.003 C (B) 60 C
(C) 44 C (D) 18 C V V
62. An uncharged capacitor of capacitance 8.0 F is
connected to a battery of emf 6.0 V through a resistance (A) (B)
of 24 , then
(i) the current in the circuit just after the connections O t O t
are made is :
(A) 0.25 A (B) 0.5 A
(C) 0.4 A (D) 0 A
(ii) the current in the circuit at one time constant after V V
the connections are made is :
(A) 0.25 A (B) 0.09 A (C) (D)
(C) 0.4 A (D) 0 A
63. An uncharged capacitor of capacitances 12.0 F is O t O t
connected to a battery of emf 6.00 V and internal
resistance 1.00  through resistanceless leads. At 12.0
s after the connections are made :
 CAPACITOR 7
CAPACITOR WITH DIELECTRIC 75. A condenser is charged and then battery is removed.
A dielectric plate is put between the plates of
67. The distance between the plates of a parallel plate condenser, then correct statement is
condenser is d. If a copper plate of same area but (A) Q constant V and U decrease
d (B) Q constant V increases U decreases
thickness is placed between the plates then the new (C) Q increases V decreases U increases
2
(D) None of these
capacitance will become-
(A) half (B) double 76. While a capacitor remains connected to a battery, a
(C) one fourth (D) unchanged dielectric slabis slipped between the plates. Then
(A) the energy stored in the capacitor decreases
68. Putting a dielectric substance between two plates of (B) the electric field between the plates increases
a condenser, the capacity, potential and potential (C) charges flow from the battery to the capacitor
energy respectively- (D) the potential difference between the plates is
(A) Increases, decreases, decreases changed
(B) Decreases, increases, increases
77. In a parallel plate capacitor of capacitance C, a metal
(C) Increases, increases, increases
sheet is inserted between the plates, parallel to them.
(D) Decreases, decreases, decreases
The thickness of the sheet is half of the seperation
69. A parallel plate condenser is connected to a battery of between the plates. The capacitance now becomes
e.m.f. 4 volt. If a plate of dielectric constant 8 is inserted (A) C/4 (B) C/2 (C) 2C (D) 4C
into it, then the potential difference on the condenser
78. The plates of parallel plate capacitor are charged upto
will be-
100 V. A 2 mm thick plate is inserted between the
(A) 1/2 V (B) 2V (C) 4V (D) 32V
plates. Then to maintain the same potential difference,
70. In the above problem if the battery is disconnected the distance between the plates is increases by 1.6 mm.
before inserting the dielectric, then potential difference The dielectric constant of the plate is-
will be- (A) 5 (B) 1.25 (C) 4 (D) 2.5
(A) 1/2 V (B) 2V (C) 4V (D) 32V
79. When a slab of dielectric material is introduced
71. A parallel plate condenser with plate separation d is between the parallel plates of a capacitor which
charged with the help of a battery so that U0 energy is remains connected to a battery, then charge on plates
stored in the system. A plate of dielectric constant K relative to earlier charge-
and thickness d is placed between the plates of (A) Is less
condenser while battery remains connected. The new (B) Is same
energy of the system will be- (C) Is more
U0 U0 (D) May be less or more depending on the nature of
(A) KU0 (B) K2U0 (C) (D) the material introduced
K K2
80. Between the plates of parallel plate condenser a plate
72. In the above problem if the battery is disconnected of thickness t1 and dielectric constant K1 is placed.
before placing the plate, then new energy will be– In the rest of the space, there is another plate of
U0 U0 thickness t2 and dielectric constant k2. The potential
(A) K2U0 (B) 2 (C) (D) KU0 difference across the condenser will be-
K K
73. A parallel plate capacitor is first charged and then a Q  t1 t 2   Q  t1 t 2 
dielectric slab is introduced between the plates. The (A)    (B) 0   
A0  k1 k 2  A  k1 k 2 
quantity that remains unchanged is
(A) Charge Q (B) Potential V Q  k1 k 2  Q
(C) Capacity C (D) Energy U (C)    (D) 0 (k1t1 + k2t2)
A0  t1 t 2  A
74. When a dielectric material is introduced between the
plates of a charged condenser, the electric field 81. A sheet of aluminium is inserted in the air gap of a
between the plates parallel plate capacitor, without touching any of the
(A) decreases two plates of the capacitor. The capacitance of the
(B) increases capacitor is-
(C) does not change (A) Invariant for all positions of the sheet
(D) may increase or decrease (B) Maximum when the sheet is midway between the
2 plates
 8 Physics for NEET
(C) Maximum when the sheet is just near the +ve 88. Effective capacitance if Cair = 10 µF-
plate.
(D) Maximum when the sheet is just near the –ve
plate. K1 = 2 K2 = 4

82. The value of a capacitor formed by a thin metallic foil

is 2 µF. The foil is folded with a layer of paper having
(A) 30 µF (B) 15 µF
a thickness of 0.015 mm. The dielectric constant of the (C) 5 µF (D) 10 µF
paper is 2.5 and its breadth is 40 mm. The length of
89. While a capacitor remains connected to a battery,
the foil used is-
a dielectric slab is slipped between the plates-
(A) 0.34 m (B) 1.33 m
(A) The electric field between the plates increases
(C) 13.4 mm (D) 33.9 m (B) The energy stored in the capacitor decreases
83. A parallel plate air capacitor is charged by connecting (C) The potential difference between the plates is
its plates to a battery. Without disconnecting the changed
battery, a dielectric is introduced between its plates. (D) Charges flow from the battery to the capacitor.
As a result- 90. In a parallel plate capacitor of capacitance C, a metal
(A) P.D. between the plates increases sheet is inserted between the plates, parallel to them.
(B) Charge on the plates decreases The thickness of the sheet is half of the separation
(C) Capacitance of the capacitor decreases between the plates. The capacitance now becomes-
(D) None of the above C C
(A) (B) (C) 4C (D) 2C
84. A capacitor is charged using a battery, and battery is 2 4
withdrawn later on. Now a dielectric slab is introduced
between the capacitor plates then the correct
statement is-
(A) Q increase, V decrease, U increase
(B) Q remains constant, V increases, U decreases
(C) Q remains constant, V and U both decreases
(D) None of these
85. A parallel plate condenser with oil between the plates
(dielectric constant of oil K = 2) has a capacitance C.
If the coil is removed, then capacitance of the
capacitor becomes-

C C
(A) (B) (C) 2C (D) 2C
2 2
86. Plate separation of a 15µF capacitor is 2 mm. A
dielectric slab (K = 2) of thickness 1 mm is inserted
between the plates. Then new capacitance is given by-
(A) 15 µF (B) 20 µF
(C) 30 µF (D) 25 µF
87. The capacity of a parallel plate capacitor with no
dielectric substance but with a separation of 0.4 cm
is 2 µF. The separation is reduced to half and it is
filled with a substance dielectric of value 2.8. The
new capacity of the capacitor is-
(A) 11.2 µF (B) 15.6 µF
(C) 19.2 µF (D) 22.4 µF
 CAPACITOR 9

EXERCISE-2 4. A parallel plate air capacitor of capacitance C is con-

nected to a cell of emf V and then disconnected from it.
(Section-1 NEET/AIPMT) A dielectric slab of dielectric constant K, which can just
1. A series combination of n1 capacitors, each of value C1, fill the air gap of the capacitor, is now inserted in it.
is charged by a source of potential difference 4V. When Which of the following is incorrect ?
another parallel combination of n 2 capacitors, each of [CBSE AIPMT 2015]
value C2, is charged by a source of potential difference (A) The potential difference between the plates
V, it has the same (total) energy stored in it, as the first decreases K times
combination has. The value of C2, in terms of C1, is then (B) The energy stored in the capacitor decreases
K times
[CBSE AIPMT 2010]
2C1 n2 1 1 
(A) n n (B) 16 n C1 (C) The change in energy stored is CV 2   1
1 2 1
2 K 
n2 16C1 (D) The charge on the capacitor is not conserved
(C) 2 n C1 (D) n n
1 1 2
5. A parallel-plate capacitor of area A, plate separation d
2. Two thin dielectric slabs of dielectric constants K1 and and capacitance C is filled with four dielectric materials
K2 (K1 < K2) are inserted between plates of a parallel
having dielectric constant k1, k2, k3 and k4 as shown in
plate capacitor, as shown in the figure. The variation of
the figure below. If a single dielectric material is to be
electric field E between the plates with distance d as used to have the same capacitance C in this capacitor,
measured from plate P is correctly shown by
then its dielectric constant k is given by
P + Q
A/3 A/3 A/3

k1 k2 k3 d/2
d
+ k4
K1 K2
[CBSE AIPMT 2014]
A
(A) k = k1 + k2 + k3 + 3k4
E E
(B) k = 2 (k1 + k2 + k3 ) + 2k4
3
(A) (B) 2 3 1
0 (C) k  k  k  k  k
0 1 2 3 4
d d 1 1 1 1 3
(D) k  k  k  k  2k
1 2 3 4
E E 6. A capacitor of 2µF is charged as shown in the
figure. When the switch S is turned to position 2, the
(C) (D) percentage of its stored energy disspated is
0 0 [NEET 2016]
d d 1 2
3. A parallel plate air capacitor has capacity C, distance of
S
separation between plates is d and potential difference
V is applied between the plates. Force of attraction be-
V 2µF
tween the plates of the parallel plate air capacitor is 8µF
[CBSE AIPMT 2015]
C2 V 2 CV 2
(A) (B) (A) 20% (B) 75%
2d 2d
(C) 80% (D) 0%
CV 2 C2 V 2
(C) (D)
d 2d 2
 10 Physics for NEET
7. A capacitor is charged by a battery. The battery is re- 4. In a uniform electric field a charge of 3 C experiences a
moved and anothert identical uncharged capacitor is force of 3000 N. The potential difference between two
connected in parallel. The total electrostatic enrgy of points 1 cm apart along the electric line of force will be
resulting system [NEET 2017] (A) 10 V (B) 30 V [2014]
(A) Increasing by a factor of 4 (C) 300 V (D) 100 V
(B) Decreases by a factor of 2
(C) Remains the same 5. A parallel plate capacitor of 1F capacity is
(D) Increases by a factor of 2 discharging through a resistor. If its energy reduces
to half in one second. The value of resistance will be
8. The electrostatic force between the metal plates of an [2018]
isolated parallel plate capacitor C having a charge
2 4
Q and area A, is [NEET 2018] (A) M (B) M
n  2  n  2 
(A) proportional to the square root of the distance
between the plates.  16
(C) M (D) M
(B) linearly proportional to the distance between the n  2  n  2 
plates.
(C) independent of the distance between the plates.
6.
(D) inversely proportional to the distance between the
plates.
9V
(Section-2
NEET Booster Package)
In the given circuit, find charge on capacitor after 1s of
1. What would be the voltage across C3 ? [2010] opening the switch at t = . [2019]
=

C1
(A) 20 e–10 C (B) 25 e–10 C
(C) 30 e–10 C (D) 35 e–10 C
=

C2 7. A capacitor of capacitance 15 F having dielectric slab

of r = 2.5, dielectric strength 30 MV/m and potential
=

C3 V differene = 30 V. Calculate the area of the plate.

(C 1  C2 )V C 1V (A) 6.7 × 10–4 m2 (B) 4.2 × 10–4 m2 [2019]
(A) C  C  C (B) C  C  C –4
(C) 8.0 × 10 m 2 –4
(D) 9.85 × 10 m 2
1 2 3 1 2 3

C 2V C 3V
(C) C  C  C (D) C  C  C
2 2 3 1 2 3

2. Energy stored in between the plates of parallel plate

capacitor of area A, separated by distance d is

1 1 A
(A) 0 E 2 Ad (B) 0E 2 [2011]
2 2 d

1 A 1 Ad
(C) 0 (D) 2  E 2
2 E2 d 0

3. The diameter of the plate of a parallel plate condenser is

6 cm. If its capacity is equal to that of a sphere of diameter
200 cm, the separation between the plates of the
condenser is [2014]
(A) 4.5  10–4 m (B) 2.25  10–4 m
(C) 6.75  10–4 m (D) 9  10–4 m
 CAPACITOR 11

ANSWER KEY
EXERCISE-1

1. A 2. D 3. A 4. B 5. A 6. C 7. D 8. B 9. A 10. B 11 B 12 C 13 A
14. B 15. A 16. B 17. C 18. D 19. A 20. B 21. C 22. B 23. D 24. A 25. A 26. C
27. C 28. D 29. B 30. B 31. B 32. B 33. C 34. D 35. B 36. D 37. B 38. D 39. C
40. D 41. B 42. A 43. A 44. B 45. B 46. C 47. B 48. B 49. B 50. C 51. D 52. D
53. D 54. C 55. D 56. C 57. C 58. A 59. B 60. C 61. B 62. A 63. (i)C(ii)B(iii)C 64. C
65. A 66. C 67. B 68. A 69. C 70. A 71. A 72. C 73. A 74. A 75. A 76. C 77. C
78. A 79. C 80. A 81. A 82. D 83. D 84. C 85. A 86. B 87. A 88. A 89. D 90. D

EXERCISE-2 : PART # 1
1. D 2. C 3. B 4. D 5. C 6. C 7. D 8. C

PART # 2

1. A 2. A 3. B 4. A 5. A 6. B 7. A