Physics 9702 · AS & A Level · Potential difference and power

Potential difference and power — practice question

A battery with electromotive force (e.m.f.) $9.6\,\text{V}$ and negligible internal resistance is linked in series to two fixed resistors and a thermistor, as illustrated in Fig. 7.1. The fixed resistors have resistances of $3400\,\Omega$ and $5800\,\Omega$. The voltmeter reading in the circuit is $6.0\,\text{V}$.
(a)[2]

Calculate the current through the resistor with resistance $5800\,\Omega$.

(b)[2]

Calculate the thermistor resistance.

(c)[2]

The battery initially stores $2.6 \times 10^{4}\,\text{J}$. Assume the battery e.m.f. stays constant. Determine the final energy stored in the battery after a charge of $330\,\text{C}$ has passed through it.

(d(i))[1]

The surroundings change so that the thermistor’s resistance increases. State whether the thermistor’s temperature decreases, increases, or stays unchanged.

(d(ii))[1]

The surroundings change so that the thermistor’s resistance increases. State whether the current in the thermistor decreases, increases or remains unchanged.

(d(iii))[1]

The surroundings change so that the thermistor’s resistance increases. State whether there is a decrease, increase or no change to the potential difference across the thermistor.

(d)[3]

The surroundings change so that the thermistor’s resistance increases. State whether there is a decrease, increase or no change to: (i) the temperature of the thermistor (ii) the current in the thermistor (iii) the potential difference across the thermistor.

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: $9.6 = 6.0 + I \times 5800$

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