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A black body of surface area 1 cm² is kept inside an enclosure held at 27 deg C, while the body itself is maintained at 327 deg C by electrical heating. Taking the Stefan constant as 6.0 x 10⁻⁸ W m⁻² K⁻⁴, what electrical power is required to keep its temperature steady?

1. 0.73 W
2. 0.85 W
3. 0.97 W
4. 1.21 W

Correct answer: 0.73 W

Solution

The net Stefan-Boltzmann radiation loss for the body equals about 0.73 W, which the electrical input must supply.

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