Question

The electrostatic potential V at a point on the circumference of a thin non-conducting disk of radius r and uniform charge density $\sigma$ is given by equation V = $4\sigma r$. Which of the following expression correctly represents electrostatic energy stored in the electric field of a similar charged disk of radius R?

• A. U = $\frac{8}{3}\pi\sigma^2R^3$
• B. U = $\frac{4}{3}\pi\sigma^2R^3$
• C. U = $\frac{2}{3}\pi\sigma^2R^3$
• D. None of these

Answer 1

Answer: (C)

U = $\frac{2}{3}\pi\sigma^2R^3$

Answer 2

The electrostatic energy stored in the electric field of a uniformly charged thin non-conducting disk of radius R and uniform charge density $\sigma$ is given by the standard formula:

$U = \frac{2\pi \sigma^2 R^3}{3\epsilon_0}$

Comparing this with the given options, and assuming the options are missing the factor $1/\epsilon_0$, option (C) matches the standard result. The given potential formula for the circumference is likely extraneous or incorrect.