Energy and voltage in circuits

The resistance of a thermistor is affected by its temperature. A student investigates this relationship using the circuit shown below.

Circuit schematic

The student uses a voltmeter to measure the voltage across the thermistor. Explain how the voltmeter should be connected to the circuit.

[1]

Explain how the student can work out the resistance of the thermistor using this circuit.

[2]

The student places the thermistor in a beaker of water of varying temperature to carry out the experiment.

The depth of immersion of the thermistor in the water is always kept constant at 4 cm.
The student stirs the water continuously to ensure uniform temperature.
The student adjusts the variable resistor to keep the current very small to avoid internal heating of the thermistor.

The independent variable in this experiment is

[1]

A controlled variable in this experiment is

[1]

The diagram below shows how the student views a thermometer to read the temperature of the water.

Thermometer line of sight

Suggest how the student can improve this technique to obtain a more accurate temperature reading while using the same thermometer.

[1]

The table shows the student's results.

Temperature ( $∘C^\circ\text{C}$ )	Resistance of thermistor ( $Ω\Omega$ )
15	2400
25	1650
35	1150
45	800
55	580
65	420

Describe the relationship between the resistance of the thermistor and its temperature.

[2]

Temperature (

∘C^\circ\text{C}

)

Resistance of thermistor (

Ω\Omega

)

2400

1650

1150

800

580

420

Energy and voltage in circuits Questions