Question

A dipole with a dipole moment of magnitude p is in stable equilibrium in an electrostatic field of magnitude E . Find the word done in rotating this dipole to its position of unstable equilibrium.

Answer 1

For stable equilibrium the angle between p and E , θ₁ = 0°

For unstable equilibrium,θ₂ = 180°
Work done in rotating the dipole from angle θ₁ to θ₂
W = pE(cosθ₁-cosθ₂) = pE(cos0°-cos180°)
= 2pE.

Answer 2

Hi friend,

The work done in rotating the dipole is

W= P× E Cos (theta)

For stable it moves on uniform direction :- at 0°

For unstable it rotates at 180°

:-W= PE [cos theta (1)-cos theta(2)]

W=PE( cos 0°- cos 180°)

W= PE (1-(-1)

W= 2PE

Hope this helped you a little!!!