This is a traditional piece of equipment for demonstrating the effect of a current flowing in a conductor in the presence of a magnetic field (Lorentz or Laplace force). Connection is made via the 4mm sockets attached to the side rails. When a current of up to 8A flows the crossbar rolls one way or the other under the action of the electro-magnetic force. With clearly labelled poles to the magnet. A low voltage bench power supply is required.