Electrostatics & Capacitance (Basic Level)

Electrostatics & Capacitance (Basic Level)

1. If a glass rod is rubbed with silk it acquires a

positive charge because:

(a) Protons are added to it

(b) Protons are removed from it

(c) Electrons are added to it

(d) Electrons are removed from it

2. If the radii of a solid and a hollow sphere are

same which one can hold greater charge?

(a) Solid sphere

(b) Hollow sphere

(c) Both will hold equal charge

(d) None of the above

3. Two bodies of metal are mounted on glass-

stands. Their surface areas are equal, but one is

a sphere and the other is pear-shaped. Both are

given the same amount of electric charge. Which

one will lose its charge first?

(a) Sphere (b) Pear-shaped

(c) The question is irrelevant as both will lose

their charge in equal time

4. A positively charged body is brought near an

uncharged gold leaf electroscope; then:

(a) No charge is induced in the leaves

(b) Positive charge is induced in both the

leaves

(c) Negative charge is induced in both the

leaves

(d) Positive charge is induced in one leaf and

negative in the other

5. Select the correct alternative:

(a) The charge gained by the uncharged body

form a charged body due to conduction is

equal to charge initially present.

(b) The magnitude of charge increases with the

velocity of charge.

(c) Charge can not exist without matter

although matter can exist without charge

(d) Attraction is the true test of electrification

6. The force between two electrons separated by a

distance r varies as:

(a) r2 (b) r

(c) r-1 (d) r-2

7. There are two charges +1 micro coulomb and –5

micro coulomb; the ratio of forces acting on them

will be:

(a) 1 : 5 (b) 1 : 1

(c) 5 : 1 (d) 1 : 25

8. Two particles having charges q1 and q2 when

kept at a certain distance, exert a force F on

each other. If the distance between the two

particles is reduced to half and the charge on

each particle is doubled the force between the

particles would be:

(a) 2F (b) 4F

(c) 8F (d) 16F

9. Four charges are

arranged at the

corners of a square

ABCD as shown in

Fig. .The force on a

charge kept at the

center O is:

(a) Zero

b) Along diagonal AC

(c) Along diagonal BD

(d) Perpendicular to the side AB

9. Two particles A and B having equal charges are

placed at a distance d apart. A third charged

particle placed on the perpendicular bisector at a

distance x will experience the maximum

Coulomb’s force when:

(a) (b) x=d/2

(c) (d)

12. Three charges +4q, Q and q are placed in a

straight line of length at points distant 0, /2

and respectively. What should be the value of

Q in order to make the net force on q to be zero?

(a) -q (b) -2q

(c) -q/2 (d) 4q

13. A sphere of radius R has a uniform distribution

Electrostatics & Capacitance (Basic Level)

of electric charge in its volume. At a distance x

from its center of x < R, the electric field is

directly proportional to :

(a) 1/x2 (b) 1/x

(c) x (d) x2

15. The electric field inside a spherical shell of

uniform surface charge density is : .

(a) Zero (b) Constant

(c) Proportional to the distance from

the center

(d) None of the above

16. +Q charge is present at the points A, B, C of a

triangle having equal limbs. The intensity of

electric field at O will be:

(a)

(b)

(c) Zero

(d)

17. The magnitude of electric field strength E such

that an electron placed in it would experience an

electrical force equal to its weight is given by:

(a) mge (b) mg/e

(c) elmg (d) e2g/2m

18. If the electric field intensity in a fair weather

atmosphere is 100V/m, radius of the earth is

6400 km, then the total charge on earth’s

surface is:

(a) 4.55x106C (b) 4.55x107C

(c) 4.55x108C (d) 4.55x109C

19. The fig. Is a plot of lines of

force due to two charges q1

and q2. Find out the sign of

charges:

(a) both negative

(b) upper positive and lower negative

(c) both positive

(d) upper negative and lower positive

20. The fig. Shows electric lines of force. If EA and

EB are electric fields

at A and B and

distance AB = r, then:

(a) EA > EB

(b) EA = EB/r

(c) EA < EB

(d) EA > EB/r2

21. A charge is placed at the centre of a cube with

side L. The electric flux linked with cubical

surface is:

(a) (Q/6L2o) (b) (Q/L2o)

(c) (Q/o) (d) Zero

22. Total electric flux coming out of a unit positive

charge put in air is:

(a) o (b) o–1

(c) (4o)–1 (d) 4o

23. A hollow metal sphere of radius 5 cm is charged

such that the potential on its surface is 10 volt.

The potential at the centre of the sphere is:

(a) Zero

(b) 10 volt

(c) Same as at a point 5 cm away from the

surface

(d) Same as at a point 25cm away from the

centre

24. A charge Q is placed at the center of a circle of

radius R. The work done in moving a charge q

from A to B so as to complete a semicircle is:

(a) Zero

(b)

(c)

Electrostatics & Capacitance (Basic Level)

(d)

25. In bringing an electron towards another electron,

electrostatic potential energy of the system:

(a) Decreases

(b) Increases

(c) Becomes zero

(d) Remains same

26. An electric dipole placed in a uniform electric

field experiences, in general:

(a) A force and a torque

(b) A force only

(c) A torque only

(d) Neither a force nor a torque

27. The work done in deflecting a dipole through

180o from field direction is:

(a) pE (b) 2pE

(c) ½pE (d) Zero

28. 1000 small water drops each of radius r and

charge q coalesce together to form one

spherical drop. The potential of the bigger drop

is larger than that of the smaller ones by a

factor:

(a) 1000 (b) 100

(c) 10 d) 1

29. Increasing the charge on the plates of a

capacitor means: .

(a) Increasing the capacitance

(b) Increasing the potential difference between

the plates

(c) Decreasing the potential difference

between the plates

(d) No change in the field between

the plates

30. In order to increase the capacity of a parallel

plate condenser one should introduce between

the plate a sheet of:

(a) Mica

(b) Tin

(c) Copper

(d) Stainless steel

31. If E is the field between the plates of a parallel

plate capacitor, the electrostatic energy per unit

volume is:

(a) oE (b) oE2

(c) ½oE2 (d) o/2E2

32. Two capacitors of equal capacities are

connected in series, they have some resultant

capacity. Now they are connected in parallel.

The resultant capacity becomes:

(a) Four times of the previous value

(b) One fourth of the previous value

(c) Twice of the previous value

(d) Half of the previous

value

33. Five capacitors of 10µF

capacity each, are

connected to a D.C.

potential of 100V as shown in the Fig. The

equivalent capacity between the points A and B

will be:

(a) 40µ F

(b) 20µ F

(c) 30µ F

(d) 10µ F

34. Three identical capacitors are connected

together differently. For the same voltage to

every combination, the one that stores

maximum energy is:

(a) The three in series

(b) The three in parallel

(c) Two in series with the third in

parallel with it

(d) Two in parallel with the third in

series with it

35. Three capacitors each of value 3µF are

available. The minimum and maximum

capacitance which may be obtained by use of

these are:

(a) 1µF and 9µF

Electrostatics & Capacitance (Basic Level)

(b) 3µF and 9µF

(c) 3µF and 6+µF

(d) 1µF and 6µF

36. Two metal plates form a parallel plate

condenser. The distance between the plates is

d. A metal plate of thickness d/2 and of the same

area is inserted completely between the plates.

The ratio of capacitances in the two cases (late

to initial) is:

a) 2 : 1 (b) 1 : 2

(c) 1 : 1 (d) 1 : 4

37. When a soap bubble is charged, its size

(a) Increases

(b) Decreases

(c) remains the same

(d) increase if it is given positive charge and

decreases if it is given negative charges.

38. Three charges 2q – q, –q are located at the

vertices of an equilateral triangle. At the circum

centre of the triangle.

(a) The field is zero but potential is non –zero

(b) The field is non-zero but potential is zero

(c) Both, field and potential are zero

(d) Both, field and potential are non zero.

39. The variation of potential with distance R from a

fixed point is as shown in the figure.

The electric field at R = 5m is

(a) 2.5 volt/m (b) –2.5 volt/m

(c) 2/5 volt/m (d) –2/5 volt./m

40. The dielectric constant K of an insulator cannot

be

(a) 3 (b) 6

(c) 8 (d)

41. Certain substances lose their electrical

resistance at very low temperature. These

substances are called

(a) Good conductors

(b) Semi-conductors

(c) Super conductors

(d) Dielectrics

42. A charged particle of mass m and charge q is

released from rest in an electric field of constant

magnitude E. The kinetic energy of the particle

after time t is

(a) (b)

(c) (d)

43. Electric lines of force about a negative point

charges are

(a) circular, anticlockwise

(b) circular, clockwise

(c) radial, inwards

(d) radial, outwards

44. The electric potential at the surface of an atomic

nucleus (Z=50) of radius 9.0 x 10–13 cm is

(a) 80 volts (b) 8 x 106 volt

(c) 9 volt (d) 9 x 105 volt

45. An electric dipole consists of two opposite

charges each of magnitude 1.0 x 10–6 coulomb

separated by a distance of 2.0 cm. The dipole is

placed in an external field of

The maximum torque on

the dipole is

(a) 0.2 x 10–3 newton – metre

(b) 1.0 x 10–3 newton – metre

(c) 2.0 x 10–3 newton – metre

1 2 3 4 5 6

1

2

3

4

5

Electrostatics & Capacitance (Basic Level)

(d) 4.0 x 10–3 newton – metre

46. Five balls, numbered 1 to 5 are suspended using

separate threads. Pairs (1,2) (2,4), (4,1) show

electrostatic attraction, while pairs (2,3) and (4,5)

show repulsion. Therefore ball 1 must be

(a) Positively charged

(b) Negatively charged

(c) Neutral

(d) Made of metal

47. A given charge is situated at a certain distance

from an electric dipole in the end-on position,

experienced a force F. If the distance of the

charge is doubled, the force acting on the

charge will be

(a) 2 F (b)

(c) (d)

48. A particle A has a charge + q and particle B has

charge + 4q with each of them having the same

mass m. When allowed to fall from rest through

the same electrical potential difference, the ratio

of their speeds will become

(a) 2 : 1 (b) 1 : 2

(c) 1 : 4 (d) 4 : 1

49. Two free protons are kept at a distance of 1 Å

and released, then the K.E. of each proton when

at infinite separation is

(a) 5.6 x 10–12 Joule (b) 11.5 x 10–19 Joule

(c) 23 x 10–19 Joule (d) 46 x 10–19 Joule

50. n small drops of the same size are charged to V

volt each. If they coalesce to form a single large

drop, then its potential will be

(a) (b) Vn

(c) Vn1/3 (d) Vn2/3

51. A positively charged ball hangs from a silk

thread. We put a positive test charge q0 at a

point and measure , then it can be predicted

that the electric field strength E

(a)

(b)

(c)

(d) cannot be estimated

52. A charge q1 exerts some force on a second

charge q2. If a third charge q3 is brought near

them, force of q1 exerted on q2.

(a) Will decrease in magnitude

(b) Will increase in magnitude

(c) Will remain unchanged

(d) Will increase of q3 is of the same sign as q1

and will decrease of q3 is of opposite sign

53. The energy of a charged condenser is

(a) (b)

(c) 2 CV2 (d) 2 CV

54. The capacity of a parallel plate condenser is C.

Its capacity when the separation between the

plates is halved, will be

(a) 4C (b) 2C

(c) (d)

55. Two capacitors each of 1F capacitance are

connected in parallel and are then charged by

200 volts D.C. supply. The total energy of their

charges in joule is

(a) 0.01 (b) 0.02

(c) 0.04 (d) 0.06

56. A capacitance of a spherical conductor of radius

r is (in C.G.S. egm)

(a) r (b)

(c) r2 (d)

Electrostatics & Capacitance (Basic Level)

57. The energy stored in a condenser of capacity C

which has been raised to a potential V is given

by

(a) (b)

(c) (d)

58. In a charged capacitor, the energy resides in

(a) the positive charges

(b) both the positive and negative charges

(c) the field between the plates

(d) around the edge of the capacitor plates.

59. Force acting upon a charged particle kept

between the plates of a charged capacitor is F.

If one of the plates of the capacitor is removed,

force acting on the same particle will become

(a) 0 (b)

(c) F (d) 2F

60. The capacitor of 1F is charged to 100 V and

then disconnected from the power supply.

Another uncharged capacitor of 4F is now

connected across it. The common voltage

across the combination would be

(a) 25 V (b) 33.3 V

(c) 20 V (d) 80 V

61. Three capacitors each of capacity 1F are

connected in parallel. To this combination a

fourth capacitor to capacity 1 F is connected in

series. The resultant capacity of the system is

(a) 4 F (b) 2 F

(c) (d)