An electric dipole having dipole moment of magnitude p is placed in a uniform electric field having magnitude E. What is the magnitude of the greatest change in potential energy that can happen for this dipole in this field? Why?

(a) pE
(b) 2pE
(c) 4pE
(d) 0.5 pE

Explanation:

The formula for the potential energy of a dipole placed in an electric field is given by

U = - pE Cos θ

where, θ is the angle between dipole moment and the electric field vector.

For θ = 0°,

initial potential energy, Ui = - pE

For θ = 180°,

final potential energy, Uf = - pE Cos 180 = pE

Change in potential energy

ΔU = Uf - Ui

ΔU = pE - (-pE)

ΔU = 2pE

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