Question

If we have a charged hollow sphere, charged solid sphere, charged disc, and a charged squared plate having charge Q, then in which case will force be maximum on a point charge +q when kept on the surface.

• A. Charged Hollow Sphere
• B. Charged Solid Sphere
• C. Charged Disc
• D. Charged Squared Plate

Answer 1

Answer: (D)

charged squared plate

Answer 2

The force on a point charge $q$ is $F=qE$. For a conductor, the electric field $E = \sigma/\epsilon_0$ where $\sigma$ is the surface charge density. Charge accumulates at points of higher curvature (sharper points) on a conductor, leading to higher $\sigma$ and thus higher $E$ at these points. Among a sphere, disc, and square plate, the square plate has the sharpest points (corners), where charge density will be highest, resulting in the maximum electric field and thus maximum force.