Answer Happy

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(a) Figure 1 shows the apparatus used to obtain the data needed to calculate the resistance of a thermistor at different temperatures. Figure 1 Power supply I I= 0.025A (A V = 9.0V Thermometer 20°C- Water- Thermistor Bunsen burner (0) In the box below, draw the circuit symbol for a thermistor. (1) (ii) Use the data given in Figure 1 to calculate the resistance of the thermistor at 20 °C. Use the correct equation from the Physics Equations Sheet. Resistance = ohms (2)

(iii) Figure 2 shows the axes for a sketch graph. Complete Figure 2 to show how the resistance of the thermistor will change as the temperature of the thermistor increases from 20 °C to 100 °C. Figure 2 Resistance in ohms Temperature in °C (1) (iv) Which one of the following is most likely to include a thermistor? Tick (✓) one box. An automatic circuit to switch a plant watering system on and off. An automatic circuit to switch an outside light on when it gets dark. An automatic circuit to switch a heating system on and off. (1) (b) The ammeter used in the circuit has a very low resistance. Why is it important that ammeters have a very low resistance? (1)