To investigate the variation of the resistance of a thermistor with temperature
The electrical resistance of a thermistor depends on its temperature. In this experiment a thermistor is connected to an ohmmeter to measure its resistance. The temperature of the thermistor is then slowly incresed by placing it in a test tube of glycerol which is, in turn, placed in a beaker of water which is heated with a bunsen burner. The water is heated slowly and resistance readings are taken at a number of different steady temperatures. The resistance of the thermistor drops very quickly with increasing temperature so take resistance readings after small temperature increases at the start of the experiment.
Procedure:
- Record the starting temperature and the resistance reading in a table as shown below
- Press "Apply Heat"
- After a rise of approx. 5 degrees press "Remove Heat". Wait until the temperature stops rising. Record the temperature and resistance values
- Repeat steps 2 and 3 until you have recorded at least six sets of readings. Larger temperature increases (10C) or more can be used as the experiment proceeds.
- To repeat the experiment press "Reset" and repeat the experiment procedure.
Analysis:
Temp. of thermistor (8C) Resistance (V)
Plot a graph, on graph paper, of resistance (y-axis) against temperature
Precautions:
- Check for the resistance of the connecting leads and contacts on the ohmmeter. Subtract from later readings
- Heat very slowly to try to maintain thermal equilibrium between the water and glycerol and coil. When the bunsen is removed wait until the temperature is steady before taking the resistance readings
- Use glycerol in the test tube as it is a better heat conductor than water
