Moving magnet and conductor problem

A thought experiment in which a magnet and conductor move relative to each other, producing the same induced current although classical electromagnetism assigns different causes to the two arrangements.

Connect

Faraday's law of induction: A law stating that changing magnetic flux through a circuit induces an electromotive force. It predicts the circuit response in both arrangements, even when the proposed causes differ.
Albert Einstein: A theoretical physicist whose work reshaped modern physics, including special relativity. He opened his 1905 relativity paper by describing this induction puzzle.
Electric field: A field that exerts force on electric charges, whether or not they are moving. The moving-magnet account invokes an electric field where the moving-conductor account invokes magnetic force.
Magnetic field transformation: The relativistic mixing of electric and magnetic field components between inertial reference frames. It explains how a field that is magnetic in one frame can include an electric component in another.
Lorentz force: The force on a charged particle due to electric and magnetic fields. In the moving-conductor arrangement, magnetic force on moving charges drives the current.
On the Electrodynamics of Moving Bodies: Albert Einstein's 1905 paper introducing the special theory of relativity. Its opening discussion presents the magnet-and-conductor asymmetry as a problem to resolve.
Magnetic field: A field produced by currents, magnetic materials, and changing electric fields that acts on moving charges. Classical descriptions assign the relevant field action differently depending on which object moves.
Field strength tensor: The antisymmetric tensor encoding electric and magnetic fields in relativistic electrodynamics. Its unified representation replaces the impression that electric and magnetic causes are fundamentally separate.
Electromotive force: The energy supplied per unit charge around a circuit, including contributions from electric fields and non-electrostatic forces. It gives one circuit-level quantity for comparing the two distinct induction mechanisms.
Special relativity: A theory of space and time in which physical laws are the same in all inertial frames and light has invariant speed. Relativity removes the privileged rest frame implied by the differing classical explanations.