Post on 29-Mar-2015
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)