Q.
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 $A,$ midway between the two charges $+ q$
A) Zero
B) $\frac{1}{4\pi\varepsilon_{0}}\frac{2q}{L}\left( 1 + \sqrt{5} \right)$
C) $\frac{1}{4\pi\varepsilon_{0}}\frac{2q}{L}\left( 1 + \frac{1}{\sqrt{5}} \right)$
D) $\frac{1}{4\pi\varepsilon_{0}}\frac{2q}{L}\left( 1 - \frac{1}{\sqrt{5}} \right)$
Explanation
(d) $V = \frac{2q}{4\pi\varepsilon_{0}L} - \frac{2q}{4\pi\varepsilon_{0}L\sqrt{5}} = \frac{2q}{4\pi\varepsilon_{0}L}\left\lbrack 1 - \frac{1}{\sqrt{5}} \right\rbrack volt$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.