An electric dipole is formed by two particles fixed at the ends of a light rod of length `I`. The mass of each particle is `m` and charges are `-q` and `+q`The system is suspended by a torsion less thread in an electric field of intensity `E` that the dipole axis is parallel to the field if it is slightly displaced the period of angular motion is

Options

A. `1/(2pi) sqrt((2qE)/(ml))`
B. `2pi sqrt((ml)/(qE))`
C. `2pi sqrt((ml)/(qE))`
D. `1/(2pi) sqrt((ml)/(4qE))`

Answer

C

Explanation

`tau=PEsin theta , tau =I alpha, Ialpha =PE sin theta`
I= moment of inertia `=(ml^(2))/2`
`:.` Time period `=2pi sqrt(I/(pE))`