Question

Define torque acting on a dipole of dipole moment placed in a uniform for lectic field. Express its vector form and point out the direction in which act

Answer 1

torque acting on a dipole moment placed in a uniform electric field is TORQUE=FORCE*DIPLACEMENT

τ=dQEsin theta

diole moment is given by 

p=qd

and the direction of the dipole moment is from the positive to the negative charge

Answer 2

Consider an electric dipole AB placed in an uniform electric field making an angle theta with direction of electric.

Due to the electric field it will feel a torque which is given by:

Torque = force× perpendicular distance

T = qE × BC

Since sintheta = BC/2l

BC =2l sin theta

Torque = qE ×2l sintheta

Put p=q×2l

Torque = pE sintheta.

In vector form:

T^_ = p ×E^_

It goes from (-)ve to (+)ve direction.