An electric dipole is placed at an angle of `30^(@)` with an electric field intensity `2xx10^(5)N//C`. It experiences a torque equal to `4Nm`. The charge on the dipole, if the dipole is length is `2 cm`, is

Options

A. 8 mC
B. 4mC
C. 6mC
D. 2mC

Answer

D

Explanation

Torque, `tau = pE sin theta`
`4 = p xx 2 xx 10^(5) xx sin 30^(@)`
or `p = (4)/(2 xx 10^(5) xx sin 30^(@)) = 4 xx 10^(-5)C m`
Dipole moment `p = q xx l`
`:. q = (p)/(l) = (4 xx 10^(-5))/(0.02) = 2 xx 10^(-3) C = 2 mC`.