Fig. 6.1 shows the circuit symbol for a relay and two labelled terminals. [Figure 6.1]

1. (a)By referring to Fig. 6.1, explain the effect of a current passing from A to B.[2]
2. (b)Fig. 6.2 shows two circuits linked by a relay. The heater transfers energy at a rate of 40W when it is connected to a 12V supply. [Figure 6.2] Switch S is closed. The variable resistor is adjusted so that its resistance R increases from 0. Fig. 6.3 shows how the power transferred in the 40W heater varies as R increases from 0. The graph shows a sharp decrease when the resistance R reaches RH. [Figure 6.3] Explain the shape of the graph in Fig. 6.3.[3]
3. (c)(i)The 40W heater connected to the 12V supply is switched on. Calculate: the energy transferred in the heater in 2.0 minutes energy = ............................................................. J[2]
4. (c)(ii)the resistance of the heater. resistance = ........................................................ Ω[3]

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