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. `(1)/(4pi epsilon_(0))(2L)/(L) (1+(1)/(sqrt(5)))`
B. `(1)/(4pi epsilon_(0))(2L)/(L) (1-(1)/(sqrt(5)))`
C. zero
D. `(1)/(4pi epsilon_(0))(2L)/(L) (1+sqrt(5))`

Answer

B

Explanation

`V = (1)/(4pi epsilon_(0)) (q)/(r )`
Here, the electric potential at point `A`
`V = 2V_(+Ve) + 2V_(-Ve)`
`V = (1)/(4pi epsilon_(0)) [(2q)/(L)-(2q)/(Lsqrt(5))]`
`V = (2q)/(4pi epsilon_(0)L) (1-(1)/(sqrt(5)))`