Annealing by short circuit is a method of efficiently annealing copper wire which employs a controlled electrical short circuit.
It can be advantageous because it does not require a temperature-regulated furnace like other methods of annealing.
The two pulleys have an electrical potential across them, which causes the wire to form a short circuit.
The Joule effect causes the temperature of the wire to rise to approximately 400 °C.
Therefore, the speed with which the wire can be drawn through varies quadratically as the voltage applied.