Code Number: 6B40.10

Demo Title: Variac and Light Bulb

Condition: Good

Principle: Radiant Color vs. Temperature

Area of Study: Astronomy

Equipment:

Light bulbs (1000 W), Socket, Variac.

Procedure:

See also: 6B40.10 in Astronomy.

Put the 1 KW light bulb onto the variac and turn up slowly. At low voltages the large filament area should look red to a dull orange. As you now slowly turn up the voltage the filament will get hotter and the corresponding color will be more and more towards white.

References:

D. C. Agrawal, Harvey S. Leff, and V. J. Menon, "Efficiency and Efficacy of Incandescent Lamps", AJP, Vol. 64, #5, May 1996, p. 649.

Video Credit: Jonathan M. Sullivan-Wood.

6B40.10 - Variac & Light Bulb

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6B40.10 - Variac and Light Bulb

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