A sphere of surface area 1.25 m² and emissivity 1.0 is at a temperature of 100°C.At what rate does it radiate heat into empty space? (σ = 5.67 × 10^-8 W/m² ∙ K⁴) A)7.1 W B)0.71 mW C)1.4 kW D)9.9 mW E)3.7 W

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Quizplus · Accepted Answer

The rate of heat radiation is given by the Stefan-Boltzmann law: P = εσAT⁴. Here, ε = 1, σ = 5.67 × 10⁻⁸ W/m²∙K⁴, A = 1.25 m², and T = 373 K (100°C in Kelvin). Calculating gives P ≈ 1.4 kW.

A Sphere of Surface Area 1