Question

Four point charges 2*10^-9C, 1*10^-9C, -2*10^-9C, 3*10^-9C are placed at the corners of a square of side length √2m. What is the electric potential at the center of the square?

(a) 36V

(b) -36V

(c) 2*10^-9V

(d) Zero

I got this question by my college director while I was bunking the class.

Origin of the question is Potential Energy of a System of Charges topic in chapter Electrostatic Potential and Capacitance of Physics – Class 12

Answer 1

Correct option is (a) 36V

The explanation is: Distance of the center of the square from the corner points=√2*\(\frac {\sqrt 2}{2}\)m=1m. Therefore, electric potential at the center of the square due to the charges = V=\(\frac {1}{4\pi \epsilon} \frac {(2*10-9+1*10-9-2*10-9+3*10-9)}{1}\)=9*10^9*(2*10-9+1*10-9-2*10-9+3*10-9)=9*(2+1-2+3) =36V.