Question

An electric dipole of magnitude $17 \times 10^{-8} C - m$ is aligned in a uniform electric field of $2 \times 10^{5} N / C$. What is value of potential energy of the dipole to hold the dipole at $30^{\circ}$ with the direction of electric field?

• A. $-1.7 \times 10^{-3} J$
• B. $-1.7 \times 10^{-2} J$
• C. $-2.9 \times 10^{-2} J$
• D. $5.1 \times 10^{-2} J$

Answer 1

Answer: (C)

$\ P E =-P E \cos \theta $
$=-17 \times 10^{-8} \times 2 \times 10^{5} \times \cos 30^{\circ} $
$=-17 \sqrt{3} \times 10^{-3} $
$=-2.9 \times 10^{-2} J $