Electrostatics – Electrostatic Potential, Potential Energy and Capacitance Quiz - ICSE Class 12 Physics
Free practice quiz: Electrostatics – Electrostatic Potential, Potential Energy and Capacitance (ICSE Class 12 Physics). 14 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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Two point charges, +q and -q, are separated by a distance d. The electric potential at the midpoint of the line joining them is:
- kq/d
- -kq/d
- 0
- 2kq/d
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Answer: C. 0
The potential due to +q at the midpoint is V1 = kq/(d/2) = 2kq/d. The potential due to -q at the midpoint is V2 = k(-q)/(d/2) = -2kq/d. The total potential at the midpoint is V_total = V1 + V2 = 2kq/d - 2kq/d = 0.
When a dielectric material is inserted between the plates of a charged parallel plate capacitor, its capacitance:
- Decreases
- Increases
- Remains unchanged
- Becomes zero
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Answer: B. Increases
When a dielectric material with dielectric constant K is inserted between the plates of a parallel plate capacitor, the capacitance becomes C' = KC, where C is the original capacitance. Since K > 1 for dielectric materials, the capacitance increases.
The electric field inside a hollow conducting sphere with a charge Q on its surface is:
- kq/r^2
- kq/r
- Zero
- kQ/(4πr^2)
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Answer: C. Zero
For a conductor in electrostatic equilibrium, the electric field inside the conductor is always zero. This is because charges on a conductor redistribute themselves until the net electric field inside is zero.
The work done to move a charge q from infinity to a point with electric potential V is:
- qV
- -qV
- V/q
- q/V
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Answer: A. qV
The electric potential V at a point is defined as the work done per unit charge to bring a positive test charge from infinity to that point. Therefore, the work done (W) to move a charge q from infinity to that point is W = qV.
Which of the following statements about equipotential surfaces is incorrect?
- Electric field is perpendicular to equipotential surfaces.
- Electric field is parallel to equipotential surfaces.
- Equipotential surfaces are closer where the electric field is stronger.
- No work is done in moving a charge along an equipotential surface.
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Answer: B. Electric field is parallel to equipotential surfaces.
The electric field is always perpendicular to equipotential surfaces. This is because the potential difference along an equipotential surface is zero, and the component of the electric field parallel to the surface would do work if a charge were moved along it. The other statements are correct.