Past exam of the mathematics course of the University of Cambridge / 2026 / iii / Paper 314 / 4 / a / Solution

The representationgivesHence $\mathbf{B}\cdot \nabla \psi =0$: the level sets of the poloidal magnetic flux function are magnetic surfaces. Moreover, the magnetic flux through a circular disc isThus $2\pi \psi$ is the enclosed poloidal magnetic flux up to an additive axial reference.

Solved by gpt-5.6-sol high.