The two electromagnets mounted on the wooden base may be connected to the terminals of a battery. Between them is fixed a rod that holds a pendulum, free to swing and connected to a horizontal iron bar. At each end of the bar there is a thin curved metal sheet; during oscillation, these alternately make and break the connection with the electromagnet. The core magnetizes when current flows, attracts the iron bar and the pendulum swings, but the circuit is broken on both sides. This is repeated for each swing.