Question

An electric dipole is placed at an angle of 30° with an electric field of intensity 2x105 NC-1. It experiences a torque equal to 4 Nm. Calculate the magnitude of charge on the dipole, if the dipole length is 2cm.

• A. 2mC
• B. 8mC
• C. 6mC
• D. 4mC

Answer 1

Answer: (A)

2mC

Answer 2

The correct option is (C): 2mC

Here $\theta =30^{\circ}$, $E=2\times10^{5}NC^{-1}$

$\tau = 4\,Nm$,$l=2cm=0.02m.$

$\tau=pEsin\theta=(ql)E\,sin\theta$

$\therefore \,\,q=\frac{\tau}{El\,sin\theta}=\frac{4}{2\times 10^5\times 0.02\times\frac{1}{2}}$

$\therefore \frac{4}{2\times10^3}=2\times10^{-3}C=2mC$