Question

A charge $+Q$ at $A$ (see figure) produces electric field E and electric potential $V$ at D. If we now put charges $-2 Q$ and $+ Q$ at $B$ and $C$ respectively, then the electric field and potential at D will be

• A. $E$ and 0
• B. 0 and $V$
• C. $\sqrt{2} E$ and $\frac{ V }{\sqrt{2}}$
• D. $\frac{ E }{\sqrt{2}}$ and $\frac{ V }{\sqrt{2}}$

Answer 1

Answer: (A)

When charges $-2 Q$ and $+Q$ are placed at $B$ and $C$ respectively,
$V'=\frac{1}{4 \pi \varepsilon_{0}}\left[\frac{Q}{a}-\frac{2 Q}{a}+\frac{Q}{a}\right]=\text { zero }$
This settles in favour of (a).