A student investigates how the resistance of a negative temperature coefficient (NTC) thermistor changes with temperature.
Which of these is the correct circuit symbol for a thermistor?
The student places the thermistor inside a beaker of hot water and allows it to cool down to room temperature, recording the temperature of the water.
Explain why the student must stir the water continuously before taking each reading.
To determine the resistance of the thermistor, the student also uses a voltmeter and an ammeter. State how the voltmeter and the ammeter should be connected relative to the thermistor.
The table below shows the student's results.
| Temperature (∘C^{\circ}\text{C}∘C) | Resistance (Ω\OmegaΩ) |
|---|---|
| 80 | 150 |
| 70 | 240 |
| 60 | 380 |
| 50 | 950 |
| 40 | 900 |
| 30 | 1350 |
| 20 | 1900 |
Identify the anomalous reading in the table, giving its temperature and resistance.
State the expected range of resistance at this temperature if it followed the trend shown by the other data points.
Why is it difficult to obtain reliable temperature and resistance readings very close to the boiling point of water (e.g., above 95∘C95^{\circ}\text{C}95∘C)?
Suggest one way the student could vary the temperature of the water/thermistor without waiting for the water to cool naturally.
