Practise explaining relay switching through an electromagnet and recognising relays and loudspeakers as applications of the magnetic effect of current.
The electric starter motor in a car is switched on and off using a relay.
The relay consists of a plastic case and two flexible springy strips, X and Y, which are made of soft iron. These iron strips act as the switch when a circuit is connected between the terminals W and Z.
Fig. 7.1 shows \(\mathrm{X
Fig. 7.2 shows the equipment from Fig. 7.1 inside a magnetising coil. The magnetising coil is in series with the 12 V car battery and switch S , which is open.
Switch S is now closed.
Explain what happens to the springy iron strips X and Y .