Physics 5054 · O Level · Electromotive force and potential difference

Electromotive force and potential difference — practice question

Fig. 7.1 illustrates two circuit components: a thermistor and an LDR. Fig. 7.2 presents a battery connected to a diode, an ammeter and a resistor. Fig. 7.3 gives the current-voltage graph for the diode.
(a)[2]

For each of these components state the factor that increases its resistance. thermistor LDR

(b(i))[1]

State what is meant by the electromotive force (e.m.f.) of the battery.

(b(ii))[2]

Explain why the e.m.f. of the battery must be greater than 5.4 V.

(b(iii))[2]

Calculate the electrical energy supplied to the resistor in 5.0 minutes.

(b(iv))[1]

The circuit is wired again with the diode facing the opposite way, as shown in Fig. 7.4. Explain what is observed.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Reduced thermistor temperature / cooling of thermistor” …

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