CAIE IGCSE Physics 4.3.1.2 Circuit Diagrams Containing Diodes and Questions

Practise interpreting diode and LED circuits, including one-way current, reverse bias and rectified a.c. output graphs.

Exam points

explain why an LED lights only when forward biased
choose the current or p.d.-time graph produced by a diode with an a.c. supply
interpret four-diode circuits to decide current direction through a resistor

[Maximum number: 1]

Fig. 6.1 shows the circuit diagram for a flashlight (torch).

Fig. 6.1

The electromotive force (e.m.f.) of the battery is 4.5 V . The circuit contains a $60 \Omega$ fixed resistor. The current in the light-emitting diode (LED) is 0.020 A .

Explain why the LED does not light up if the battery is reversed.

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CAIE IGCSE Physics 4.3.1.2 Circuit Diagrams Containing Diodes and Questions question 1