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## Homework Statement

Show that the energy of an ideal dipole

**p**in an electric field

**E**is given by

U = -

**p ⋅ E**

## Homework Equations

Work = θτ where τ is torque

τ =

**p × E**

## The Attempt at a Solution

U = ∫(

**p × E**) dθ' (from θ to 0, since the dipole will eventually align itself with the magnetic field.)

=∫pE(sinθ')dθ'

=-pE(cosθ') with limits θ to 0

=-pE + pE(cosθ)

=

**p ⋅ E**- pE

That's not what I needed to prove. Help?