📌 Answer:

Definition: An <b>equipotential surface</b> is one where the <b>electric potential is the same</b> at every point.

Key Reasoning:

Work done = W = q × ΔV

On an equipotential surface:
ΔV = V₂ − V₁ = 0

Therefore:
W = q × 0 = <b>0</b>

Additional Reasoning:
• The electric force is always <b>perpendicular</b> to the equipotential surface.
• A perpendicular force does <b>no work</b> along the surface.

∴ No work is done in moving a charge along an equipotential surface.