Practice question

**Electric dipole** consists of charges +q and -q separated by 2a, dipole moment p = q·2a, vector from negative to positive, unit C·m. In uniform field E, torque τ = p × E, magnitude τ = p E sinθ, tending to align p with E, potential energy U = -p·E = -p E cosθ. tau = p E sin θ . tau = 7 × 10⁻⁹ × 9 × 10⁴ × sin 45° = 63 × 10⁻⁵ × (√(2)/2) = 4.45 × 10⁻⁴ N m . Substituting values gives 4.45 × 10⁻⁴ N m, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and