Question

For the given arrangement of charges, charges $1$ and $2$ are fixed. A third charge at mid of line joining charges $1$ and $2$ is kept. Net force on third charge is directed toward original position if it is displaced along

• A. equatorial line
• B. axial line
• C. None of these
• D. Both $a$ and $b$

Answer 1

The correct option is A equatorial line

When displaced along axial line:Here, $F_{32}>F_{31}$
$\Rightarrow {\overrightarrow{F}}_{net}={\overrightarrow{F}}_{32}-{\overrightarrow{F}}_{31}$
$($away from the original position$)$

When displaced along equatorial line:
Here, ${\overrightarrow{F}}_{net}={\overrightarrow{F}}_{32}+{\overrightarrow{F}}_{31}$
$($toward the original position$)$

Hence, option $\left(b\right)$ is correct.