In empty space, Ampere's law alone implies that a unidirectional magnetic field must also be uniform (independent of position).

Question

Quizplus · Accepted Answer

Ampere's law states that the line integral of the magnetic field around a closed loop is equal to the current passing through the loop. In empty space, there are no currents, so the line integral of the magnetic field must be zero. This implies that the magnetic field must be uniform.

In Empty Space, Ampere's Law Alone Implies That a Unidirectional