In one minute

Christof Baumgärtel and Simon Maher devise a new experiment on unipolar induction, the effect known as Faraday's paradox. Whether the magnetic field rotates with the magnet or stays still has long been debated, with evidence on both sides. Their apparatus is the first to include the relative motion of the measurement circuit and its closing wires, as well as the magnet and disc, using a rotatable amplifier circuit with an LED output. The results show the closing wire must be treated as part of the problem, which resolves the apparent paradox. Which field picture holds cannot yet be told apart, and the authors propose direct electron interaction as the route to settling the remaining questions.

Resolving the paradox of unipolar induction: new experimental evidence on the influence of the field