Question

An electric dipole, consisting of two opposite charges of $2 \times 10^{-6} \, C$ each separated by a distance 3 cm is placed in an electric field of $2 \times 10^5 \, N/C$. Torque acting on the dipole is

• A. $12 \times 10^{-1} N m $
• B. $12 \times 10^{-2} N m $
• C. $12 \times 10^{-3} N m $
• D. $12 \times 10^{-4} N m $

Answer 1

Answer: (C)

Charges $(q) = 2 \times 10^{-6} \, C$, Distance (d)
$= 3 cm = 3 \times \, 10^{-2} \, m$ and electric field (E)
$= 2 \times 10^5 \, N/C$. Torque ($\tau$) = q.d.
$E =(2 \times 10^{-6}) \times (3 \times 10^{-2}) \times (2 \times 10^5)$
$= 12 \times 10^{-3}\, Nm$