Nov
22
What is the temperature of a flashlight bulb filament when turned on?
ByA common flashlight bulb is rated at 0.2A and 2.9V. If the resistance of the bulb’s tungsten filament at room temperature (20°C) is 1.10Ω, estimate the temperature of the tungsten filament when the bulb is turned on.
3 Comments
November 22nd, 2009 at 8:25 am
Tungsten (W) 20C when the bulb is turned on it will take seconds for it to heat up. Praise St Jude.
November 22nd, 2009 at 8:57 am
At full brightness (a few milliseconds after turning on) the filament temperature will be around 4000 degrees fahrenheit.
November 22nd, 2009 at 9:42 am
I would try this. Calculate rated resistance using E = IR (solve for R). Assume that the increase in resistance for tungsten is linear (in the range of interest). Form a ratio of room temperature resistance / room temperature in degrees Kelvin (use absolute temperature) = rated resistance / unknown temperature x. Convert x to degrees C. Good luck.