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AS Physics coursework

I need an explanation about why you need a fixed resistor in a circuit with a thermistor to measure the voltage across it. It was due yesterday :s-smilie:

Reply 1

Mehh

jabab

I need an explanation about why you need a fixed resistor in a circuit with a thermistor to measure the voltage across it. It was due yesterday :s-smilie:

You don't. What you do need is to either measure the voltage across the thermistor and limit the current flowing through it, or limit the voltage and measure the current flowing through it. The later would result in a higher current, which equates to higher ohmic power loss.
Thus we normally limit the current and measure the voltage. By placing a battery across the thermistor we know what the voltage across the thermistor would be, 1.5V, because that is what the battery outputs. By placing a resistor in series with the thermistor the voltage across the thermistor becomes dependant on the resistance of the thermistor.