Fig. 8.1 shows the circuit diagram of a temperature gauge. It contains an ammeter, a thermistor, a fixed resistor R and a battery. [Figure 8.1] The current is measured at different temperatures and a graph of the results is shown in Fig. 8.2. [Figure 8.2]

1. (a)(i)State how the resistance of the thermistor changes with temperature and explain how Fig. 8.2 shows this change.[2]
2. (a)(ii)Resistance and current are used for the measurement of temperature. State one other physical property that is used for the measurement of temperature.[1]
3. (b)(i)A temperature scale involves the use of fixed points. State what is meant by: the ice point[1]
4. (b)(ii)the steam point.[1]
5. (c)(i)At 80°C, the potential difference (p.d.) across the thermistor is 3.6V. State what is meant by potential difference.[1]
6. (c)(ii)Calculate the resistance of the thermistor when the temperature is 80°C. resistance =[3]
7. (c)(iii)The electromotive force (e.m.f.) of the battery is 25V. Calculate the resistance of the resistor R. resistance =[2]
8. (d)(i)The current scale on the ammeter is linear. Using values from Fig. 8.2, a student marks the scale on the ammeter with temperature values that correspond to the values of the current. The temperature is then read directly from the temperature scale on the ammeter. State what is meant by a sensitive thermometer.[1]
9. (d)(ii)State and explain at which temperatures this thermometer is most sensitive.[2]
10. (e)The temperature gauge is used to measure the temperature of a room. Suggest why the temperature obtained using the gauge is slightly higher than the actual temperature of the room.[1]

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