Question

derive the expression of torque acting on a dipole in a uniform electric field
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Answer 1

Answer:

Consider a dipole with charges +q and −q farming a dipole since they are a distance (d) from each other and makes an angle θ with electric field.

The force on the charge is,

i)

F

−

=−qE

ii)

F

+

=+qE

And the parallel component cancel out each other because of equal magnitude and opposite direction.

∴ The perpendicular component adds, which results into,

F

=

F

0

sinθ+

F

+

sinθ

=2qEsinθ

and we know torque,

C

=F× distance b/w force

=(2qEsinθ×d)

and dipole moment, p=2qd

⇒

C

=P.Esinθ {Hence Proved}