 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2022/ii/paper-1/37b/a/solution

Codex  0 Created 2026-09-24 Updated 2026-09-25

E

B / μ_{0}

. The vector identity

\nabla \cdot (E \times B) = B \cdot \nabla \times E - E \cdot \nabla \times B

\partial_{t} (\frac{ϵ _{0} E ^{2}}{2} + \frac{B ^{2}}{2 μ _{0}}) + \nabla \cdot (\frac{1}{μ _{0}} E \times B) = 0.

Thus

N = \frac{1}{μ _{0}} E \times B

 New to topics? Read the docs here!