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Cal Poly Pomona
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Physics Demonstrations at Cal Poly Pomona

Demo Index:
    EM-D-BR
Pira Index:
    5D 20.00
Title:
    RESISTANCE OF A LIGHT BULB--COOLING
Description:
    Demonstrates that cooling a hot filament lowers the resistance to current flow.
Equipment:
    1. Bulb & bare filament apparatus
    2. 2 B-A leads:
    3. Edison cell battery


    (SEE EM-D-RL)
Procedure:
    1. Connect as shown. Start with the alligator ends across 4 cells of the battery to see if you can only dimly see the small bulb light. If not try 5 cells.
    2. When bulb glows dimly, blow gently across the exposed filament.
    3. As that filament cools, decreasing the resistance, the small bulb glows more brightly.