Question

An electric dipole consists of two opposite charges, each of magnitude $1.0\, \mu C$ separated by a distance of $2.0\, cm$. The dipole is placed in an external electric field of $10^5\, N \,C^{-1}$. The maximum torque on the dipole is

• A. $0.2 \times 10^{-3}\, N\,m$
• B. $1 \times 10^{-3}\, N\,m$
• C. $2 \times 10^{-3}\, N\,m$
• D. $4 \times 10^{-3}\, N\,m$

Answer 1

Answer: (C)

Here, $\tau_{max}=pEsin90^{\circ}$
$=q\left(2a\right)E=10^{-6}\times2\times10^{-2}\times10^{5}$
$=2\times10^{-3}\,N\,m$.