CBSE Class 12 · 2010 · ElectrostaticsVery Short Answer

In which orientation, a dipole placed in a uniform electric field is in
(i) stable,
(ii) unstable equilibrium?

Solution

The torque on a dipole is

τ = pE sin θ

and its potential energy is

U = - pE cos θ

. At

θ = 0^{\circ}

the energy is minimum, so the dipole is in stable equilibrium (aligned with

E

). At

θ = 18 0^{\circ}

the energy is maximum, so it is in unstable equilibrium (anti-aligned with

E

CBSE Class 12 Board · 2010 · Subjective

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