(i) Obtain the expression for the torque \overrightarrow{\tau} experienced by an electric dipole of dipole moment \overrightarrow{p} in a uniform electric field, \overrightarrow{E}. (ii) What will happen if the field were not uniform?

CBSE Class 12 Physics 2017 Delhi Set 3 Paper - Question 5

Question : 5 of 8

Marks: +1, -0

(i) Obtain the expression for the torque

{τ}↖{→}

experienced by an electric dipole of dipole moment

{p}↖{→}

in a uniform electric field,

{E}↖{→}

.
(ii) What will happen if the field were not uniform?

Solution:

(i) Obtaining of the expression for torque experienced by an electric dipole
(ii) Effect of non-uniform electric field
(i)

Force on

+q, {F}↖{→}=q {E}↖{→}

Force on

-q, \;\; {F}↖{→}=-q {E}↖{→}

Magnitude of torque

τ\;=q E × 2 a sin \;θ

\;=2 q a E sin \;θ

{τ}↖{→}\;={p}↖{→} × {E}↖{→}

(ii) If the electric field is non uniform, the dipole experiences a translatory force as well as a torque.

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