(a(i))[1]
On Fig. 8.1, draw a circle round the output device.
(a(ii))[2]
State the purpose of this circuit.
(b(i))[3]
The resistors X and Y each have resistance $R$. When it conducts, the LED labelled B emits blue light and the LED labelled G emits green light. State whether blue light or green light is produced when the resistance of component C is greater than the resistance $R_v$ of the variable resistor. Explain your answer.
(b(ii))[3]
State and explain what happens as the resistance of component C is lowered.
(c)[1]
Suggest what the function of the variable resistor is.