# Physics Questions and Answers – Electrostatics of Conductors

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This set of Physics Multiple Choice Questions & Answers (MCQs) focuses on “Electrostatics of Conductors”.

1. What is the net electrostatic field in the interior of a conductor?
a) Positive
b) Negative
c) Zero
d) Depends on the nature of the conductor

Explanation: Net electrostatic field is zero in the interior of a conductor. When a conductor is placed in an electric field, its free electrons begin to move in the opposite direction. Negative charges are induced on the left end and positive charges on the right end of the conductor. The process continues until the electric field set up by induced charges becomes equal and opposite the external field.

2. What is the electric field in the cavity of a hollow charged conductor?
a) Positive
b) Negative
c) Zero
d) Depends on the nature of the conductor

Explanation: By Gauss’s theorem, the charge enclosed by the gaussian surface is zero. Consequently, the electric field must be zero at every point inside the cavity. Then, the entire excess charge lies on its surface.

3. How is the electric field at the surface of a charged conductor related to the surface charge density?
a) Proportional to each other
b) Indirectly proportional
c) Independent
d) Exponential

Explanation: The electric field at the surface of a charged conductor is proportional to the surface charge density. The electric field is zero inside the conductor and just outside, it is normal to the surface. The contribution to the total flux comes only from its outer cross-section.

4. How is the potential within and on the surface of a conductor?
a) Indirectly proportional
b) Directly proportional
c) Zero
d) Constant

Explanation: Electric field at any point is equal to the negative of the potential gradient. But inside a conductor, the electric field is zero. Hence, the electric potential is constant throughout the volume of a conductor and has the same value on its surface.

5. What is the total work done on moving a test charge on an equipotential surface?
a) Maximum
b) Minimum
c) Constant
d) Zero

Explanation: The potential difference between any two points on an equipotential surface is zero.
Work done=Test charge x potential difference(0)
=Zero .

6. In a thunderstorm accompanied by lightning, it is safest to run near a tree or open ground rather than sitting inside a car.
a) True
b) False

Explanation: In a thunderstorm accompanied by lightning, it is safest to sit inside a car, rather than near a tree or on the open ground. The metallic body of the car becomes an electrostatic shielding from lightning.

7. ‘X’ is the phenomenon of making a region free from any electric field. Identify X.
b) Electrostatic shielding
c) Gauss theorem
d) Corona discharge

Explanation: The phenomenon of making a region free from any electric field is called electrostatic shielding. It is based on the fact that the electric field vanishes inside the cavity of a hollow conductor.

8.What type of surface is the surface of a conductor?
a) Equipotential
b)Unipolar
c) Unipotential
d) Bipolar

Explanation: Electric field at any point is equal to the negative of the potential gradient. But inside a conductor, the electric field is zero. Hence, the electric potential is constant throughout the volume of a conductor and has the same value on its surface. Thus the surface of a conductor is equipotential.

Sanfoundry Global Education & Learning Series – Physics – Class 12. 