Fig. 6.1 gives the circuit symbol for a relay, with two labelled terminals, and Fig. 6.2 presents two circuits connected through a relay. The heater transfers energy at a rate of 40 W when it is connected to a 12 V supply.
(a)[2]
By using Fig. 6.1, explain what happens when a current flows from A to B.
(b)[3]
Fig. 6.2 shows two circuits linked by a relay. Switch S is closed. The variable resistor is altered so that its resistance $R$ rises from 0.
(c)[3]
Explain why the graph in Fig. 6.3 has that shape.
(d(i))[2]
The 40 W heater on the 12 V supply is turned on. Calculate the energy transferred in the heater in 2.0 minutes.
(d(ii))[3]
Calculate the heater resistance.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Current in magnetising coil creates magnetic field” …