Temperature Scales (CIE A Level Physics)

The e.m.f generated in a thermocouple thermometer may be used for the measurement of temperature. 

Fig 1.1 shows the variation with temperature T of the e.m.f E.

Fig 1.1

By reference to Fig 1.1, explain why this thermocouple would not be suitable to measure temperature.

State two advantages and two disadvantages of using a resistance thermometer over a thermocouple thermometer to measure the temperature of an object.

Describe:

A gas, initially at a temperature of 37.2°C, is heated so that its temperature rises to 92.4°C.

Calculate, to an appropriate number of decimal places:

Suggest the most suitable type of thermometer, and describe the physical property of the material used in the thermometer, to measure:

The resistance of a thermistor is measured by placing it in three water baths at different constant temperatures.

In room temperature water (25°C), its resistance is 10.0 kΩ. In 100°C water, the resistance falls to 1.0 kΩ. In the third water bath, its resistance is 2.5 kΩ. 

Assuming that the resistance of the thermistor varies linearly with temperature, calculate the temperature of the water in the third water bath.

The temperature of the water in the third water bath, as measured on the thermodynamic scale of temperature, is 338 K.

Explain why:

Other than resistance, state two other physical properties of materials that can be used to measure temperature.

A steel manufacturer needs to decide which temperature sensor would be the most appropriate for their manufacturing process.

Fig. 1.1 shows the process of iron and steel manufacturing.

Fig. 1.1

Table 1.1 contains information about a resistance temperature detector (RTD), thermocouple and thermistor. 

Table 1.1

A thermocouple contains two junctions, a hot junction and a cold junction, sometimes referred to as a reference junction.

The manufacturer decides the best temperature sensor would be a thermocouple.

Suggest some ideal uses of a thermistor compared to a thermocouple.

An NTC thermistor is used to measure the temperature of water in an engine. The thermistor and multimeter are shown in Fig. 1.1.

Fig 1.1

Table 1.1 shows the resistance of the thermistor for different temperatures of the water in the engine. 

Using this data, plot the variation of temperature with resistance on the axes in Fig. 1.2.

Assume that the resistance of the thermistor varies linearly with temperature. 

Include error bars on your graph from the uncertainty of the multimeter. 

Use the graph in Fig 1.2 to obtain the minimum possible temperature of the water at a resistance of 6.00 kΩ.