Question

A dipole with moment p experiences a maximum torque of 4 × 10⁻²¹ N·m in a uniform electric field. What is the strength of the electric field?

Options

• E = 4 × 10⁵ N/C

• E = 1 × 10⁵ N/C

• E = 2 × 10⁵ N/C

• E = 8 × 10⁵ N/C

Answer 1

Maximum torque occurs when θ = 90°, so τ_max = pE. Given τ_max = 4 × 10⁻²¹ N·m and p = 2 × 10⁻²⁶ C·m (assumed from context), we get E = τ_max/p = (4 × 10⁻²¹)/(2 × 10⁻²⁶) = 2 × 10⁵ N/C.