O-LevelPhysicsMeasurement5054/21 · Oct/Nov 2020 · Q56 Marks

Fig. 5.1 shows some parts of a thermocouple thermometer that is being used to determine the temperature of a liquid. [Figure 5.1]

(a)Suggest an appropriate material for: • X • Y • Z.[1]
(b)(i)All types of thermometer require the measurement of a physical property that varies with temperature in order to obtain a value for the temperature. State the physical property of a thermocouple thermometer that is used in this way.[1]
(b)(ii)Discuss what is meant by the term linearity when applied to a thermocouple thermometer.[2]
(c)State two advantages of a thermocouple thermometer over a liquid-in-glass thermometer. 1. 2.[2]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

[B1] X, Y and Z to be two (or three) different metals
[B1] (output / thermoelectric) electromotive force / e.m.f. / voltage
[B1] linearity indicates whether the output (voltage) is directly proportional to something
[B1] directly proportional to the temperature difference (between the junctions)
[B2] any two from: measures rapidly varying temperatures / quick response / small heat capacity / electrical output / output can be fed directly into a computer / measures high temperatures / large range / robust / precise location / remote reading

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