to investigate the variation of the resistance of a thermistor with temperature

Question 1

explain how the student varied the temperature of the thermistor

Answer 1

place the thermistor and a sensitive thermometer into a large test tube filled with glycerol. Place this test tube in a beaker of cold water and allow the temperature as recorded by the thermometer to give a steady reading. Turn on the heat source and allow an increase in temperature of about 5C, then remove the heat source, wait for the thermometer’s temperature to stop rising and record the temperature

Question 2

how was the resistance measured?

Answer 2

by using an ohmmeter, taking into account the resistance of the ohmmeter probes themselves.

Question 3

using the recorded data, plot a graph to show the variation of the resistance of a thermistor with its temperature.

Answer 3

resistance vs temperature

Question 4

what does your graph tell about the relationship between the resistance of a thermistor and its temperature?

Answer 4

the graph is a downward sloping line, which is not straight. it shows that a semiconductor like a thermistor decreases rapidly with increasing temperature.

Question 5

in this investigation, why is the thermistor usually immersed in oil rather than in water?

Answer 5

glycerol is a better heat conductor than water- it maintains better thermal contact with the wire- water would form small bubbles of gas at the wire. glycerol also has a lower specific heat capacity

Question 6

what errors should be avoided?

Answer 6

heat the water slowly to avoid overheating the glycerol
measure the resistance of the ohmmeter wires.
parallax error when reading the thermometer.