Question

An electric field of $1000\text{V/m}$, is applied to an electric dipole moment of ${10}^{-29}C\cdot m.$ What is the potential energy of the electric dipole?

• A. $-10\times {10}^{-29}J$
• B. $-7\times {10}^{-27}J$
• C. $-9\times {10}^{-20}J$
• D. $-20\times {10}^{-18}J$

Answer 1

The correct option is B $-7\times {10}^{-27}J$

Potential energy of a dipole is given by,

$U=-\overrightarrow{P}\cdot \overrightarrow{E}$
$=-PE\cos \theta$

$\text{Where,}\theta =\text{angle between dipole moment vector and the field}$

$U=-\left({10}^{-29}\right)\left({10}^3\right)\cos {45}^{\circ }\approx -7\times {10}^{-27}\text{J}$

Hence, $\left(B\right)$ is the correct answer.