A blackened solid copper sphere of radius 2 cm is placed in an evacuated enclosure whose walls are kept at 100°C. At what rate must energy be supplied to the sphere to keep its temperature constant at

Question

A blackened solid copper sphere of radius 2 cm is placed in an evacuated enclosure whose walls are kept at 100°C. At what rate must energy be supplied to the sphere to keep its temperature constant at 127°C? Stefan constant = $5.67 \times 1 0^{- 8}$ J m⁻² K⁻⁴.

Answer:

1.78

Solution:

$P = σ \cdot 4 π r^{2} (T^{4} - T_{0}^{4}) = 5.67 \times 1 0^{- 8} \times 4 π 0.02^{2} (40 0^{4} - 37 3^{4}) = 1.78$ W.

TestHub · Accepted Answer

P = σ ⋅ 4 π r 2 ( T 4 − T 0 4 ​ ) = 5.67 × 1 0 − 8 × 4 π 0.02 2 ( 40 0 4 − 37 3 4 ) = 1.78 W.

Physics - Heat & Thermo Question with Solution | TestHub

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