An NTC thermistor is used in a circuit that monitors the temperature inside a fridge.
The Table shows how the resistance of the thermistor changes with temperature.
Table
| Temperature in ∘C^\circ\text{C}∘C | Resistance in Ω\OmegaΩ |
|---|---|
| 0 | 3200 |
| 10 | 2000 |
| 20 | 1250 |
| 30 | 800 |
| 40 | 530 |
Describe how the resistance of the thermistor changes as the temperature increases.
Use data from the Table in your answer.
The thermistor is connected in series with an ammeter and a 6.0 V power supply.
The ammeter reads 3.0 mA.
Use the equation: potential difference=current×resistance\text{potential difference} = \text{current} \times \text{resistance}potential difference=current×resistance
Calculate the resistance of the thermistor and use the Table to find its temperature.
The reading on the ammeter increases.
State what has happened to the temperature in the fridge. Explain your answer.
Suggest one other use of a thermistor in a circuit.
42 exam-style questions on OCR GCSE Physics 3.2 Simple circuits, covering 3.2.1 Series and parallel circuits, 3.2.2 Circuit symbols and circuit diagrams, 3.2.3 Current, potential difference and resistance, 3.2.4 Ohm's law, 3.2.5 Ohmic and non-ohmic resistors, 3.2.6 Designing circuits to investigate resistance, 3.2.7 Linear and non-linear circuit components, 3.2.8 Current-potential difference graphs for components, 3.2.9 Resistance in series and parallel, 3.2.10 Series and parallel circuit problems, 3.2.11 Circuits for measurement and testing, 3.2.12 Power transfer in circuit devices, and 3.2.13 Energy and power in resistor circuits. Each one has a worked solution and a mark scheme showing where the marks go.