In this experiment you will investigate the resistance of a thermistor at different temperatures. You are provided with: • a power source • a switch • a voltmeter with two leads that may be connected between different points in the circuit shown in Fig. 2.1 • a thermistor placed inside an empty beaker • a 220 Ω resistor • a stirring thermometer • a supply of hot water from the supervisor • paper towels to mop up spillages. The supervisor has set up the circuit shown in Fig. 2.1. [Figure 2.1]

1. (a)(i)Measure the room temperature θR and record it on the answer line. θR = ................................... °C Close the switch. Record the potential difference across the thermistor VXY while the thermistor is at room temperature θR in Table 2.1 on page 6. Open the switch. [1][1]
2. (a)(ii)Disconnect the voltmeter from points X and Y. Reconnect the voltmeter across the 220 Ω resistor between points Y and Z. Close the switch. Record the potential difference across the 220Ω resistor VYZ while the thermistor is at room temperature θR in Table 2.1 on page 6. Open the switch. [1][1]
3. (b)(i)Disconnect the voltmeter from points Y and Z. Reconnect the voltmeter across points X and Y. Ask your supervisor to pour hot water into the beaker until it is about half full. Carefully place the thermometer in the hot water and stir the water gently. Wait for about 30 s. Measure the temperature of the hot water θH and record it on the answer line. θH = ................................... °C [1][1]
4. (b)(ii)Close the switch. Record the new potential difference VXY while the thermistor is at the temperature of the hot water θH in the bottom row of Table 2.1. Open the switch. [1][1]
5. (c)Disconnect the voltmeter from points X and Y. Reconnect the voltmeter across the 220Ω resistor between points Y and Z. Close the switch. Record the new potential difference VYZ while the thermistor is at the temperature of the hot water θH in the bottom row of Table 2.1. Open the switch. Hold the thermistor by its connecting leads and carefully remove it from the hot water. Place it on the bench away from the rest of the circuit. [1][1]
6. (d)(i)Explain why you waited for 30s before measuring the temperature of the hot water. [1][1]
7. (d)(ii)Explain why you stirred the water before reading the temperature of the hot water. [1][1]
8. (e)The current I in the circuit is calculated using the equation I = VYZ / R where R = 220 Ω. Use your measurements recorded in Table 2.1 to calculate the current I at room temperature θR and at the temperature of the hot water θH. Record your answers in Table 2.1. [1][1]
9. (f)The resistance RT of the thermistor is calculated using the equation: RT = VXY / I Use your data in Table 2.1 to calculate RT at room temperature θR and RT at the temperature of the hot water θH. RT at room temperature θR = ................................... Ω RT at temperature of the hot water θH = ................................... Ω [1][1]
10. (g)Calculate α, the average change in the resistance per degree Celsius for the thermistor as its temperature rises from room temperature θR to the temperature of the hot water θH. Use the equation shown. α = change in resistance of thermistor / change in temperature α = ................................... Ω/°C [1][1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.