Question

Two point charges $Q$ and $-3Q$ are placed certain distance apart. If the electric field at the location of $Q$ be $\overrightarrow{E}$, then that at the location of $-3Q$ will be :

• A. $3\overrightarrow{E}$
• B. $-3\overrightarrow{E}$
• C. $\overrightarrow{E}/3$
• D. $-\overrightarrow{E}/3$

Answer 1

Answer: (D)

Step 1: $E$ is electric field due to charge $-3Q$ at the location of $Q$
$<br/>E=\frac{1}{4\pi {ϵ}_0}\frac{3Q}{x^2}\dots ..(1)<br/>$
Step 2: $E^{\prime }$ is electric field due to charge $Q$ at the location of $-3Q$
$<br/>E^{\prime }=\frac{1}{4\pi {ϵ}_0}\frac{Q}{x^2}\dots ..(2)<br/>$
From equation (1) and (2)
$<br/>E^{\prime }=\frac{E}{3}<br/>$