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light blub problem

O

Omegachi

Diamond Member
so if there is a 60W lightbulb and its running at 110V AC... the resistance should be 201ohms right? because P=V^2/R

but when i measure the bulb's resistence, it shows about 16.5 ohms... why is that?
 
Originally posted by: Omegachi
so if there is a 60W lightbulb and its running at 110V AC... the resistance should be 201ohms right? because P=V^2/R

but when i measure the bulb's resistence, it shows about 16.5 ohms... why is that?
Click to expand...


Resistance increases as temperature goes up. Tungsten filaments get VERY hot.

Edit: BTW, the increase is linear: R=R0+aT, where a is the thermal resistence coefficient. Typical incandescent bulbs heat the tungsten in the 5800+ degree farenheit range.
 
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