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 m C
B. 4 m C
C. `8 mu C`
D. 2 m C

Answer

D

Explanation

Torque, `vec(tau)= vec(p) xx vec(E) = p E 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) Cm `
Dipole moment, ` p = q xx l `
`q = (p)/(l) = (4 xx 10^(-5))/( 0 . 02) - 2 xx 10^(-3) C = 2 m C`