Physics Dept. Demonstration Manual

DEM20 - Temperature Coefficient of Resistance

Objective:

To show how resistance of an electrical conductor will increase with an increase of temperature.

 
Apparatus:  
  • Resistance demonstrator
  • Power supply (Anatek 25-2D)
  • Propane gas tank, with valve and hose
  • Large Analog Ammeter, 0-2 Amp DC (Triplett 726)


Method:

The resistance wire coil (mounted above a burner) is connected in series with the Ammeter and Power supply. While the coil is cold, current is adjusted to 2 Amps, or full scale. When the burner is ignited, current flow will rapidly drop to approximately 40% of full scale, due to increased resistance of the wire coil at a higher temperature.

Note:

Do not attempt to use a lamp as an indicator of current. (A lamp filament behaves like a negative resistance as voltage decreases, masking the desired effect).