Four identical charges q are placed at the corners of a square of side a. Find the potential energy of one of the charges due to the remaining charges.
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Explanation

The electric potential of point A due to the charges placed at B, C and D is
`V = (1)/(4pi epsilon_(0)) (q)/(a) + (1)/(4pi epsilon_(0))(q)/(sqrt(2)a) + (1)/(4pi epsilon_(0)) (q)/(a) = (1)/(4pi epsilon_(0)) (2+(1)/(sqrt(2)))(q)/(a)`
`:.` Potential energy of the charge at A is = qV
`= (1)/(4pi epsilon_(0)) (2+(1)/(sqrt(2)))(q^(2))/(a)`