A student is investigating the properties of a semiconducting diode. This diagram shows the circuit she builds.

a i. Sketch a graph to show how the current in the diode would vary as the voltage across it is increased from 0 V to 1.0 V.

ii. The supply is now connected in the reverse direction and once more the potential difference across the diode is increased from 0 V to 1.0 V.

Complete the I–V graph.

b. Suggest why the safety resistor is required.

c. When the potential difference across the safety resistor is 1.4 V, the current in it is 20 mA. Calculate the resistance of the safety resistor.

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variable power supply A safety resistor Figure 10.16 >