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Fig. 3.1 shows how the resistance of a thermistor varies with temperature - OCR - A-Level Physics A - Question 4 - 2012 - Paper 1
Question 4
Fig. 3.1 shows how the resistance of a thermistor varies with temperature. The thermistor is used in the potential divider circuit of Fig. 3.2 to monitor the temper... show full transcript
Worked Solution & Example Answer:Fig. 3.1 shows how the resistance of a thermistor varies with temperature - OCR - A-Level Physics A - Question 4 - 2012 - Paper 1
Step 1
State and explain how the current I in the circuit changes as the thermistor is heated.
Answer
As the thermistor is heated, its resistance decreases. According to Ohm's Law, the current in the circuit can be expressed as:
where V is the voltage supply (6.0 V) and R is the total resistance in the circuit, which includes the thermistor's resistance.
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Decrease in Resistance: When the temperature increases, the resistance of the thermistor drops. For example, if the resistance decreases from 200 Ω (at a lower temperature) to a much lower value when heated, the current will increase accordingly.
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Change in Current: As the thermistor resistance decreases, the current through the circuit increases. This is due to the fixed voltage supply remaining constant while the resistance is variable. Therefore, for any decrease in the resistance of the thermistor, the current can be expected to rise.
In conclusion, as the thermistor heats up, the current I in the circuit increases due to the decrease in the thermistor’s resistance.