Fig. 9.1 shows a circuit that includes an LED and two resistors arranged in parallel, each with resistance $R$. The LED has a normal working voltage of $2.1\,\text{V}$ and a normal current of $0.19\,\text{A}$.
(a(i))[1]
The potential difference (p.d.) across the LED is measured using a voltmeter. On Fig. 9.1, draw the symbol for this voltmeter in the circuit.
(a(ii))[1]
The current in the LED is measured using an ammeter. On Fig. 9.1, draw the symbol for this ammeter in the circuit.
(b)[5]
Calculate the value of $R$ when the LED is operating normally.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Voltmeter linked across LED” …