The filament temperature of a light bulb is 2000 K when the bulb delivers 50 W of power.If its emissivity remains constant,what power is delivered when the filament temperature is 2500 K?
A) 122 W
B) 62 W
C) 98 W
D) 50 W

Question

Quizplus · Accepted Answer

The power radiated by a black body is proportional to the fourth power of its temperature (Stefan-Boltzmann law). If the temperature increases from 2000 K to 2500 K, the power increases by a factor of (2500/2000)^4 = 1.953125. Therefore, the new power is 50 W * 1.953125 = 97.65625 W, which is approximately 122 W.

The Filament Temperature of a Light Bulb Is 2000 K