Question

A dipole of dipole moment $\overset{ \rightarrow }{p}=p\hat{i}$ lies along the $x$ -axis in a non-uniform electric field $\overset{ \rightarrow }{E}=\frac{c}{x}\hat{i}$ . The force acting on the dipole is

• A. zero
• B. $-\frac{p c}{x^{2}}\hat{i}$
• C. $\frac{p c}{x^{2}}\hat{i}$
• D. $-\frac{p c}{2 x^{2}}\hat{i}$

Answer 1

Answer: (B)

The force acting on a dipole is
$\overset{ \rightarrow }{F}=\overset{ \rightarrow }{p}\frac{\partial E_{x}}{\partial x}$
$\overset{ \rightarrow }{F}=\overset{ \rightarrow }{p}\frac{d}{d x}\left(\frac{c}{x}\right)=-\frac{p c}{x^{2}}\hat{i}$