Resistance and Temperature in a Thermistor;  The Solid State
Obj: Determine temp-resistance properties of semiconductors

Materials:  10K thermistor (Radio Shack Part No. 271-110A) , hot plate, multimeter, thermometer, ice

Procedure
1.  Prepare an ice bath in a large beaker and record the temperature.
2.  Connect the thermistor to the multimeter to record the resistance on the proper scale.
3.  Insert the thermistor into the ice bath and allow the temperature to reach equilibrium.
4.  Record the starting temperature and resistance, then plug in the hot plate. 
5.  Record the resistance and temperature at 5.0^oC intervals to a maximum of 90^oC, stirring gently to prevent uneven heating.
6.  Plot a graph of resistance (Ω) vs. temperature (x-axis).

Analysis
1.  How does a thermistor differ from a true Ohmic resistor?  (See Lab No. ___)
2.  Describe the relationship shown on the graph.
3.  Where is your thermister most sensitive to temperature? Explain your answer.
4.  Why are semiconductor thermistors better suited for thermometers than ohmic materials?
5.  What is the resistance of your thermistor at human body temperature?
6.  Thermistors are either NTC (negative temperature coefficient) or PTC (positive temperature coefficient).  Which one was used in this lab?  How do you know?
7.  Thermistors are used in automobiles.  Suggest one possible use and describe how it works.

Back to the Brockport High School Science Department