Question

A solid sphere of radius R is charged uniformly. At what distance from its surface is the electrostatic potential half of the potential at the center?

• A. $R$
• B. $R/2$
• C. $R/3$
• D. $2R$

Answer 1

The correct option is C $R/3$

Potential at the center of sphere is $V_c=\frac{3}{2}\frac{kQ}{R}$

Potential at some distance x from center $=\frac{KQ}{x}$

$\frac{kQ}{x}=\frac{1}{2}\left(\frac{3}{2}\frac{kQ}{R}\right)$ or $x=4R/3$

Distance from surface is $x-R=R/3$