Question

A unit positive charge is moved from point A to point B by a distance of 20 cm, on an equipotential surface as shown in the figure. The work done to move this charge is:

• A. \(2 \, {J}\)
• B. \(0 \, {J}\)
• C. \(0.2 \, {J}\)
• D. \(0.02 \, {J}\)

Hint:

When moving a charge along an equipotential surface, the work done is always zero, since there is no change in potential.

Answer 1

The Correct Option is B

In this case, the charge is moved along an equipotential surface. 
By definition, an equipotential surface is a surface where the potential difference between any two points on the surface is zero. 
As a result, no work is required to move a charge between any two points on an equipotential surface. Therefore, the work done is zero: \[ W = q \cdot \Delta V \] Since \( \Delta V = 0 \) on the equipotential surface: \[ W = q \cdot 0 = 0 \, {J} \] Thus, the work done to move the charge is \( 0 \, {J} \).