Question

An electric field of $1000$V/m is applied to an electric dipole at angle of ${45}^o$. The value of electric dipole moment is ${10}^{-29}$C.m. What is the potential energy of the electric dipole?

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

Answer 1

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

$U=-\overrightarrow{P}\cdot \overrightarrow{E}$
$=-PE\cos \theta$
$=-\left({10}^{-29}\right)\left({10}^3\right)\cos {45}^o$
$=-0.707\times {10}^{-26}$J
$=-7\times {10}^{-27}$J.