CAPACITORS
1. A parallel plate air capacitor consists of two circular plates of 2m2 area separated by
1mm. If the gap between plates is doubled then its capacitance will be
1. Halved
2. Doubled
3. 4 times
4. 6 times
2. A parallel plate capacitor is charged by connecting to a battery , After charging the
battery is disconnected .Which of the following increases when plates of capacitor are
moved apart
1. Charge
2. potential
3. capacitance
4.electric field
3. A parallel plate capacitor is connected across a battery .A dielectric slab is introduced
between the plates , the battery being still connected to the plates, which of following
remains constant ?
1. charge
2. capacitance
3. electric field
4.Energy stored
4. In a charged capacitor the energy is stored in
1. the electric field between the plates
2. the edge of the capacitor
3.positive charges
4. both in positive and negative charges.
5. Two capacitors of capacitances C1 and C2 are connected in parallel. If a charge Q is given
to the combination the charge gets shared. The ratio of the charge on capacitor C1 to the
charge on capacitor C2 is
1. C1C2
2. C2 / C1
3. C1 + C2
4. C1 / C2
6. The effective capacity of two capacitors in series and parallel is 2/3 and 3 respectively.
The value of individual capacitance is
1. 2/3 and 3
2. 2 and 3
3. 1 and 2
4. 1 and 3
7. If Cs and Cp are the effective capacitances of C1 and C2 when connected in series and
parallel then
1. Cs Cp = C1C2
2. Cs + Cp = C1C2
3. Cs Cp= C1 + C2
4. Cs +Cp = C1 + C2
8. In a parallel plate capacitor of capacitance ‘C’ a metal plate is inserted between the plates
parallel to them. The thickness of plate if half of the separation between the plates . The
capacitance now is
1. 2C
2. C
3. 4C
4. C/2
9. 8 identical water droplets charged to same potential V coalesce to form a bigger drop.
The potential of the new drop will be
1. 4
2. 8
3. 6
4. 16
10. Five identical plates are connected as shown in figure to a battery . If the charge on plate
‘1’ is +q , then charges on the plates 2, 3, and 4 are
1. -2q , +2q , -2q
5
2. –q , +q , -q ,
4
3. –q , +2q , -2q
3
4. +2q , -2q , +q
2
1
11. Four metal plates each of area ‘A’ are arranged as shown. If the separation between the
plates is ‘d’ ,the equivalent capacitance between A and B is
2.
A
1.
3.
4.
B
C
12. The effective capacity between A and B in the figure is
1. 7C/4
2. 3C/4
3. 2C/3
4. 4 C/7
A
C
C
C
C
B
13. In the circuit shown the amount of charge on the plates of capacitor is
1.
2.
3.
4.
20 µ C
6 µC
4µC
8µC
5Ω
4µF
4Ω
5V
14. How many condensers of 2 µF , 250 V, are required to make a condenser of
10 µF , 1000 V,
1. 40
2. 32
3. 128
4. 80
15. A 15 µF capacitor is charged to 50 V and a 10µF is charged to 100 V. The net charge
stored in the two capacitors when they are connected in parallel is
1. 500 µC
2. 1250µC
3. 1000µC
4. 1750 µC
16. Three identical capacitors of capacitance 6µF each are connected in the form of a triangle
and a battery of 5V is connected between two of the vertices of triangle. The charge
stored in the system is
1. 40 µC
3. 20 µC
2. 30 µC
4. 45 µC
17. The insulation property of air breaks down when the electric field is 3MV/m . The
maximum charge that can be given to a sphere of diameter 10 m is approximately
1. 20 mC
2. 2 m C
3. 0.2 mC
4. 8.3 mC
18. If the charge on a body is increased by 2 µC the energy stored in it increases by 21%. The
original charge on the body is
1. 10 µC
2. 20 µC
3. 30 µC
4. 40 µC
19. A parallel plate capacitor is charged to 60µC. The plate looses charge at the rate of
3.6 x10-8 C/S. The magnitude of displacement current is
2. 3.6 x 10-8C/s
1. 1.8 x 10-8C/s
3. 4.1 x 10 -11 C/s
4. 5.7 x 10-12 C/s
20. Four identical capacitors are connected in series with a 20 V battery as shown. The point
N is earthed. The potentials at points A and B are
1. 10 V, 0 V
2. 7.5 V, -2.5 V
20V
3. 15 V , -5 V
4. 7.5 V , 2.5 V
A
B
N
21. A parallel plate capacitor is connected to a battery. The plates are pulled apart with a
uniform speed ‘v’. If ‘x’ is the separation between the plates , then the time rate of
change of the electrostatic energy of the condenser is proportional to
2.
3.
4. X
1.
22. The time in seconds required to produce a potential difference of 50 V across a capacitor
of capacitance 100 µF when it is charged at the steady rate of 500 µC/s is
1. 50
2. 10
3. 15
4. 20
23. The equivalent capacitance of the system of plates each of area ‘A’ in the figure is
A
1.
3.
2.
4.
d
11
6
3d
3A
24. The equivalent capacity between A and B in the figure is
1.
2.
3.
A
B
4.
25. In the figure point ‘C’ is grounded and the point ‘A’ is at 4000 V. The point “B’ will be
at
10µF
10µF
1. 400 V
2. 500 V
A
B
C
3. 1000 V
5µF
4. 1300 V
10µF
26. A capacitor is charged to 10V & it stores 10-3 C of charge. The capacitance of Capacitor
is
1. 10 pF
2. 100pF
3. 10x10-6 F
4. 10-4 F
27. The energy stored in a capacitor of capacity 2nF where pd is 400V is
1. 16x10-5 J
2. 16x10-6 J
3. 32x10-5
4. 32 x 10-6
28. 125 drops of water of radius 1cm each carrying a charge of 10-3 C combine to form a
single drop. By how many times the capacitance of the combined drop increases
compared to that of smaller drop.
1. 10
2. 5
3. 20
4. 25
29. Two metal spheres of radii R1 and R2 are charged to the same potential. The ratio of
charge on the two spheres is
1. R1/R2
2. R2/R1
3. R22/R12
4. R12/ R22
30. Two capacitors having capacitance 10 pF and breakdown voltage 50 V are connected in
series. The capacitance and breakdown voltage of combination will be
1. 5 pF, 50 V
2. 20 pF , 50 V
3. 5 pF , 100 V
4. 20 pF and 100 V
31. A conducting sphere of radius 10cm is charged with 10µC .Another uncharged sphere of
radius 20 cm is allowed to touch it for enough time . After two are separated the ratio of
the surface charge density is
1. 4 : 1
2. 2 : 1
3. 3 : 1
4. 1 : 1
32. Two capacitors 2 µF and 3 µF are connected in series across 100 V.
The p.d across 3 µF is
1. 40 V
2. 12 V
3. 60 V
4. 16 V
33. A condenser having a capacity 2 µF is charged to 200 volts and then the plates of
capacitor are connected by a resistance wire. The heat produced is
1. 0.004 J
2. 0.04 J
3. 0.008J
4 .0.0016 J
34. If Q denotes charge on the plates of a capacitor of capacitance C. The dimensional
formula for Q/C is
2. M1L2T-2
3. M1L1T-1
4.M1L2T-3A-1
1. M1L1T-2
35. A plane metallic sheet is given a potential of 10 V. Another plane and earthed plate of
equal area is brought very close to it. The effective potential of charged plate is nearer to
1. Zero
2. +10 V
3. -10 V
4. 20 V
36. The electric field between the plates of a capacitor with air as dielectric is ‘E’. If a
dielectric of dielectric constant 4 is placed between plates then field becomes
1. E
2. E/2
3. 2E
4. E/4
37. Total capacity of the system of capacitors shown in the figure between A and B is
2µF
1. 1 µF
A
2. 2 µF
1µF
3. 3 µF
1µF
2µF
4. 4 µF
B
2µF
38. A parallel plate capacitor consists of two metal plates each of area 1m3 separated by 0.2
cm in a dielectric of constant 4. If the capacitor is connected to a battery of 500 V , the
electric field between plates is
2. 250 K V m-1
1. 125 KVm-1
-1
3. 500 KVm
4. 62.5 K V m-1
39. A parallel plate capacitor is filled with dielectrics of dielectric constants K1 and K2
respectively. The area of each plate is ‘A’ and the separation between plates is ‘d’. the
capacitance of capacitor is given by
1.
2.
K1
K2
2
4.
3.
40. Four capacitors each of capacitance 50 µF are connected as shown in figure. If the DC
voltmeter reads 200 V , the charge on each plate of capacitor is
V
1. 2 x 10-3 C
2. 5 x 10-3 C
3. 10 mC
4. 50 mC
41. Two identical parallel plate capacitors are connected in series to a battery of emf 200 V .
A dielectric slab of dielectric constant 3 is inserted between the plates of second capacitor
The p.d. across the capacitors now is
1. 180 V , 20 V
2. 125 v , 75 V
3. 150 V , 50 V
4. 50 V , 150 V
42. A parallel plate capacitor of capacitance 4 µF if fully charged using a battery of 20 V. It
is then disconnected from the battery and connected in parallel with an uncharged
capacitor. If the common potential difference is 8 V , the capacitance of second capacitor
is
1. 6 µF
2. 10 µF
3. 12 µ F
4. 24 µF
43. If all the capacitors have capacitance ‘C’ then the
equivalent capacity between A and B is
1.
2.
3. C
A
B
4.
44. Three capacitors 3 µF , 10 µF and 15 µF are connected in series to a voltage source of
100 V. The charge on 15 µF capacitor is
1. 200 µC
2. 20 µC
3. 100 µC
4. (200/3) µC
45. When two capacitors of capacitances 5µF and 25 µF are connected in parallel and
charged using a battery, the total charge stored is 400 µC. The charge stored in 25 µC is
1. 66.66µ C
2. 33.33 µC
3. 333.3 µC
4. 666.6 µC
46. Two capacitors of 3µF and 6µF are connected in series and a P.d. of 5000V is applied
across the combination. They are then disconnected and reconnected in parallel. The P.d.
across the combination is
1. 2250 V
2. 2.25 MV
3. 1111 V
4. 1.1 MV
47. A capacitor of capacitance 4 µ F is charged to 80 V and another capacitor of capacitance
3 µF is charged to 60 V. When they are connected in parallel , the energy lost by 4 µF
capacitor is
1. 7.8 mJ
2. 4.6 mJ
3. 3.2 mJ
4. 2.5 mJ
48. In a parallel plate capacitor the distance between the plates is d= 0.2 mm. The medium
between the plates is air. The maximum potential difference which can be applied to the
capacitor is ( dielectric strength of air = 3 M V /m)
1. 3 MV
2. 300 V
10
3. 3 x 10 V
4. 600 V
49. Four capacitors with capacitances C1 = 1µF , C2 = 1.5 µF , C3 = 2.5 µF and
C4= 0.5 µF are connected as shown and are connected to a 30 V source. The potential
C2
difference between points A and B is
C1
A
1. 5 V
2. 9 V
3. 10 V
C3
C4
B
4. 13 V
50. A parallel plate capacitor with plate area ‘A’ and separation ‘d’ is filled with two
dielectric materials as shown in figure. The dielectric constants are K1 and K2 . The
capacitance will be
1.
2.
d/2
K1
K2
3.
4.
51. A capacitor of capacitance 4µF withstands a maximum voltage of 6KV, while another
capacitor of capacitance 2µF withstands 4 KV. If they are connected in series the
combination can withstand a maximum of
1. 6 KV
2.2 4 KV
3. 10 KV
4. 9 KV
52. Two capacitors 2µF and 4µ are connected in parallel. A third capacitor of 6µF is
connected in series . The combination is connected across a 12 V battery. The voltage
across 2µF capacity is
1. 2 V
2. 6 V
3. 8 V
4. 1 V
53. Three plates A,B,C each of area 50cm2 have separation 2 mm between A and B and
2 mm between B and C . The energy stored when the plates are fully charged is
1. 2 µJ
3. 5 µJ
2. 2.6 µJ
4. 2.22 µJ
A
B
1 V
C
54. A thin metal plate is inserted half way between the plates of a parallel plate capacitor of
capacitance ‘C’ in such a way that it is parallel to the two plates. The capacitance now
becomes
1. C
2. C/2
3. 4C
4. 2 C
55. Five identical capacitors when connected in series produce equivalent capacitance of
10 µF. Now these capacitors are connected so as to produce maximum value of
equivalent capacitance .The maximum value will be
1. 30 µF
2. 36 µF
3. 150 µF
4. 250 µF
56. Two capacitors of capacitances 3 µF and 6µF are charged to a potential of 12 V and 15 V
respectively. They are now connected to each other, with the positive plate of each joined
to negative plate of other. The potential difference across each will be
1. 4 V
2. 6 V
3. zero
4. 3 V
57. A parallel plate capacitor having capacitance ‘C’ has two plates of same area ‘A’ and
thickness‘t’. Figure shows the charge available on four surfaces of the plates. The
potential difference ‘V’ between the two plates is given by
1.
2.
q1 q2 q3 q4
3.
4.
+
--
58. A parallel plate capacitor has plate area ‘A’ and charge ‘Q’. The force on one plate due
to the charge on the other is (if ‘σ’ is the surface density of charge)
1.
2.
3.
4. σ A
59. Capacitance in farad of a spherical conductor having radius 2m is
1. 1.1 x10-10
2. 2.22x 10-10
3. 9 x 10-9
4. 10-3
60. A capacitor C1 = 4 µF is connected in series with another capacitor C2 = 5µF . The
combination is connected across A.C. source of 200 V. The ratio of potential difference
across C1 and C2 is
1. 5 : 4
2. 4 :5
3. 1 : 9
4. 2 :1