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Code Number: 4A30.11
Demo Title: Bimetal Strip Thermostat - Thermometer
Condition: Good
Principle: Expansion & Contraction with Temperature Variation
Area of Study: Thermodynamics
Equipment:
Bimetal strip thermometer apparatus, grill lighter, distilled water.
Procedure:
Hold the grill lighter flame under the curved part of the thermostat. After a few seconds the blue light should go out and the red light should come on. Pour distilled water over the curved part of the thermostat and this should cool it down enough to make the blue light come on again.
This thermostat is the typical home thermostat with a mercury switch atop a bimetal coil. Adjust the thermostat so that the lights are on at room temperature. Heat the coil with the flame from a grill lighter, and the coil will expand turning the lights off. Cool the coil with some water and the lights will go on again.
References:
- H. Richard Crane, "Popping Bimetal Can Keep You Warm or Cool", TPT, Vol. 36, # 5, p. 302, May 1998.
- Jay S. Huebner, "Thermal Switch Oscillators", AJP, Vol. 55, #10, Oct. 1987, p. 954.
- H- 044: "Thermostat - Auto - Stove - Bimetal", DICK and RAE Physics Demo Notebook.
- George M. Hopkins, "Simple Thermostat", Experimental Science, p 183.
- Martin C. Sagendorf, "All Matter Expands When its Thermal Energy (Temperature) is Increased", Physics Demonstration Apparatus, 2009, p. 13.
- Jodi and Roy McCullough, "Thermal Expansion with a Flashing Bulb", The Role of Toys in Teaching Physics, p. 4.128.
- C. L. Stong, "An Electrometer, a Temperature Control Apparatus, and a Simple Electric Motor", The Amateur Scientist, October, 1965.