Re: pinhole voltage

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From: Paul Doherty (pauld@exploratorium.edu)
Date: Thu Dec 09 1999 - 14:41:54 PST 

Message-Id: <l03110705b475e007f734@[192.174.2.173]>
Date: Thu, 9 Dec 1999 14:41:54 -0800
From: Paul Doherty <pauld@exploratorium.edu>
Subject: Re: pinhole voltage

Hi Kevin

The student will never get the 120 volt light to glow with 2 D cells.

The maximum voltage you can get from 2 D-Cells in series is 3 volts.

The light might glow with as few as 30 D-cells in series.

The filament of the lightbulb has a resistance. The resistance is adjusted
for a given voltage range so that the power disipated at that voltage will
heat the filament to incandescence without melting it. Use a flashlight
bulb intsead. these bulbs are designed to work on 1.5 to 12 volts.

Paul Doherty

Paul "But it is more complicated than that!" Doherty,
Senior Staff Scientist, The Exploratorium.
pauld@exploratorium.edu, www.exo.net/~pauld

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