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Re: [Shop-talk] looking for small light bulbs

Subject: Re: [Shop-talk] looking for small light bulbs
From: Steven Trovato <>
Date: Mon, 25 Feb 2008 17:43:38 -0500
Yes, yes.  I was really thinking you would just compare the 
resistance of the known bulb with the resistance of the candidate 
bulb.  The V=IR part was a not very well thought out 
afterthought.  Sorry.  In any event, I think we're overanalyzing this 
whole thing.  There are little bulbs out there of appropriate 
voltage.  Try some and find one that looks like it's the right 
brightness.  Done.


At 04:56 PM 2/25/2008, Pat Horne wrote:
>Cold resistance of a bulb is much lower than hot resistance. That's 
>why most bulbs burn out when you turn them on.
>While it may not have an exact correlation, I just measured the cold 
>resistance of a 130V 75W bulb and it measured 21 ohms. That would be 
>804 Watts cold filament dissipation. Using Ohms law, the resistance 
>of a 130V 75W lamp will be 225 ohms hot, so you might be able to 
>measure the resistance of another lamp and multiply the resistance 
>by 10 to get hot resistance, but my measurements is just a sample of one. YMMV.
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