Calculate the electric potential at a point P, located at the centre of the square of point charges shown in the figure.

Explanation

Potential at a point P is
` V = (1)/(4pi epsi_0 ) [ (q_1)/(r ) + (q_2)/(r ) + (q_3)/(r ) + (q_4)/(r ) ]`
The distance r` = (d)/(sqrt2) = (1.3)/(sqrt2) = 0.919 m`
Total charge ` = q_1 + q_2 + q_3 + q_4`
`= (12 -24 +31 +17) xx 10^(-9)`
` q = 36 xx 10^(-9)`
` therefore V = (9 xx 10^9 xx 36 xx 10^(-9))/(0.919)`
` V = 352.6V`