Two point charges-q and +q are located at points (0, 0,-a) and (0, 0, a) respectively. The electric potential at a point (0, 0, z), where z> a is

Options

A. `qa/(4pi epsilon_(0)z^(2)`
B. `qa/(4pi epsilon_(0)a`
C. `2qa/(4pi epsilon_(0)(z^(2) - a^(2))`
D. `2qa/(4pi epsilon_(0)(z^(2) + a^(2))`

Answer

( c)

Explanation

Electirc potential due to charges -q and + q at point p is given by , `V_(P) = V_(1) + V_(2)`
`rArr V_(P) = [ 1/4pi epsilon_(0) . -q/(z + a) + 1/4pi epsilon_(0) . q/(z - a) `
` = q/4pi epsilon_(0)[-1/(z+a) + 1/(z - a)] = q/4 pi epsilon_(0)[z +a-z +a/z^(2) -a^(2)]`
`= 2qa/4pi epsilon_(0)(z^(2) - a^(2))`