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## Homework Statement

The filament is 30 cm long and has a diameter of 1.5mm. The filament is drawing 15 watts and has an emissivitity of 0.9. The surroundings are at 283 k. Estimate the surface temp of the filament in K.

## Homework Equations

N = Wcycle/Qin, W cycle = Qhot - Q cold.

## The Attempt at a Solution

I'm not sure how to relate the lengths. I think 0.9= Wcycle/15 watts. But not sure what to do after I find Wcycle. Any help would be appreciated!