Four electric charges `+q, +q, -q` and `-q` are placed at the corners of a square of side 2L (see figure). The electric potential at point `A`, mid-way between the two charges `+q` and `+q`, is

Options

A. Zero
B. `1/(4pi epsilon_0) (2q)/L (1+sqrt5)`
C. `1/(4pi epsilon_0) (2q)/L (1+1/sqrt5)`
D. `1/(4pi epsilon_0) (2q)/L (1-1/sqrt5)`

Answer

D

Explanation

`V=(2Kq)/L-(2Kq)/(sqrt5L)`
`=1/(4piepsilon_0).(2q)/L[1-1/sqrt5]`