Question

An electric dipole with dipole moment 4 x 10^-9 Cm is aligned at 30° with the direction of a uniform electric field of magnitude 5 x 10⁴ NC^-1 Calculate the magnitude of the torque acting on the dipole.

Answer 1

p = 4 x 10^-9 Cm, θ = 30°, E = 5 x 10⁴ NC^-1
τ = pE sin θ = 4 x 10^-9 x 5 x 10⁴ x sin 30°
= 4 x 10^-9 x 5 x 10⁴ x \(\frac { 1 }{ 2 }\)
= 10 x 10^-5 Nm = 10^-4 Nm