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61) The dissipating factor of capacitor can be measured by using a

1. Potentiometer
2. Campbell bridge
3. Schering bridge
4. Galvanometer
EXPLANATION
No answer description required for this question.

62) The power dissipated in a pure capacitor is

1. zero
2. minimum
3. maximum
4. depends on size and voltage
EXPLANATION
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63) If Q be the charge and C be the capacity of a condenser, then the energy stored in a capacitor is given by

1. 1/2 QC
2. 1/2 QC2
3. 1/2 Q2C
4. 1/2 Q2/C
EXPLANATION
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64) 4 condensers of 4 μF each are connected in parallel. Their equivalent capacitance will be

1. 1 μF
2. 4  μF
3. 16 μF
4. 64 μF
EXPLANATION
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65) A capacitor of 40 μF is charged to a potential difference of 500 V. The charge acquired by it in coulomb is

1. 2.2
2. 2.0
3. 0.22
4. 0.02
EXPLANATION
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66) The electric flux inside a conducting sphere is

1. zero
2. uniform
3. maximum
4. minimum
EXPLANATION
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67) An electric dipole is placed in a uniform electric field at an angle θ. For what value of θ, the potential energy of the dipole is maximum

1. π
2. π/2
3. π/4
4. 0
EXPLANATION
No answer description required for this question.

68) An oil drop carries 6 electronic charges and falls with a terminal velocity in air. What magnitude of vertical electric field is required to make the drop move upward with the same speed as it was formerly moving downward ? Mass of oil drop is 1.6×10-15 kg

1. 32.7 kNC-1
2. 600 kNC-1
3. 31.7 kNC-1
4. 43.7 kNC-1
EXPLANATION
Since the drop falls with a terminal velocity, the upward force on it is equal to weight mg of the drop. In order that the drop moves upward with the same speed, a force of 2 mg must act on it in the upward direction.

2 mg = q.E

E = 2 mg/q = 2×1.6×10-15 × 9.8/6 × 1.6×10-19 = 32.7×103 NC-1 = 32.7 kNC-1

69) If a force exerted by a small spherical charged body on another object at 8 cm is 2 N, what will be the force exerted when the second object is moved to 4 cm.

1. 4 N
2. 0.5 N
3. 8 N
4. 16  N
EXPLANATION
No answer description required for this question.

70) Two plates are 1 cm apart and the potential difference between them is 10 V. The electric field between the plates is

1. 500 N/C
2. 1000 N/C
3. 10 N/C
4. 250 N/C
EXPLANATION
E = V/d = 10/1×10-2 = 1000 N/C

71) The relative permittivity of an insulator cannot be

1. 20
2. 33
3. 6
4. infinity
EXPLANATION
The relative permittivity or dielectric constant of an insulating medium is defined as the ratio of its absolute permittivity to the absolute permittivity of free space. It follows that the dielectric constant for free space is 1.

72) An electric dipole is placed in a uniform electric field in stable equilibrium. The angle between the electric dipole moment and the electric field is

1. 45°
2. 90°
3. 180°
EXPLANATION
A a dipole in stable equilibrium, when Electric filed and dipole moment are perpendicular to each other i.e. the angle between them is 0° and torque will be maximum.

73) The dielectric used in high voltage transformer is

1. mica
2. paraffin
3. porcelain
4. oiled paper
EXPLANATION
No answer description required for this question.

74) The electric potential at a point in air due to point charge is 9 V. If air is replaced by a medium of relative permittivity 3, then electric potential at that point will be

1. 27 V
2. 3 V
3. 18 V
4. 36 V
EXPLANATION
No answer description required for this question.

75) If the relative permittivity of the medium increases, the electric intensity at a point due to given charge

1. increases
2. decreases
3. remains the same
4. none of the above