(a(i))[2]
A relay is needed as part of the output device. It is not included in Fig. 6.1. Explain why a relay is required.
(a(ii))[2]
On Fig. 6.1, draw the symbol for a relay linked in the circuit as part of the output device.
(b(i))[1]
Describe the function of the variable resistor $R_v$.
(b(ii))[1]
Describe the function of the diode $D$.
(c)[3]
State whether the lamp switches on when the light level rises or when it falls. Explain your answer.