Question

A point dipole of dipole moment $p$ is placed along $y$-axis, a point charge is placed at $x$-axis at distance $r$ from point dipole, find net force on dipole due to point charge.

• A. $\frac{2kp}{r^3}{q}_0\hat{j}$
• B. $\frac{kp}{r^3}{q}_0\hat{j}$
• C. $\frac{kp}{r^3}{q}_0\hat{j}$
• D. zero because total charge on dipole is zero.

Answer 1

The correct option is C $\frac{kp}{r^3}{q}_0\hat{j}$

Force on point charge due to dipole $=q_{o}E$
$=q_o\left(\frac{kp}{r^3}\right)(-\hat{j})$
By Newton's third law
${\overrightarrow{F}}_{on-dipole}=-{\overrightarrow{F}}_{on-q_0}$
(action-raction pair)
${\overrightarrow{F}}_{on-dipole}=\frac{kp}{r^3}{q}_0(+\hat{j})$