Torque on Electric Dipole in Uniform Field (τ = pE sinθ)

jee-mainjee-advancedneet-ug

τ = pE sinθ

What each symbol means

SymbolWhat it stands for
EUniform electric field (N/C or V/m)
pElectric dipole moment (C·m)
θAngle between p and E
τTorque on dipole (N·m)

When to use this

Uniform E only. τ = 0 when p ∥ E (stable equilibrium) or p antiparallel to E (unstable). Potential energy U = −pE cosθ.