Electric Potential

An equipotential surface is defined as a surface on which the electric potential is the same at every point. The key property of equipotential surfaces is that the electric field is always perpendicular to them; no work is done in moving a charge along an equipotential surface. For a uniform electric field directed along the positive x-axis, all points sharing the same x-coordinate have the same potential, since (V = -\int E,dx) depends only on the x-coordinate. Therefore, equipotential surfaces are planes of constant x-value, which are planes parallel to the yz-plane. Option 'Parallel to the xz-plane' is incorrect because these planes contain the x-direction (field direction) and are not perpendicular to the field. Option 'Parallel to the xy-plane' is incorrect because these planes also contain the x-direction and are not perpendicular to the field. Option 'Along the direction of the field' is incorrect because no surface along the field direction can be an equipotential — the potential changes along the field. This NCERT-level conceptual question directly tests the relationship between electric field direction and equipotential surface orientation. Plausibility check: a uniform field means equally spaced parallel equipotential planes, consistent with the yz-plane orientation.