Question

A 30 kg male emperor penguin under a clear sky in the Antarctic winter loses very little heat to the environment by convection; its feathers provide very good insulation. It does lose some heat through its feet to the ice, and some heat due to evaporation as it breathes; the combined power is about 12 W. The outside of the penguin's body is a chilly −22∘C, but its surroundings are an even chillier −38∘C. The penguin's surface area is 0.56 m2, and its emissivity is 0.97. What is the rate of energy loss by radiation

Answer 1

Answer:

Rate of energy loss by radiation is 28.31 Watt

Explanation:

Given that;

m = 30 kg

power p = 12 W

emissivity e = 0.97

Surface Area A = 0.56 m²

outside of the penguin's body  T = −22°C

surroundings Temperature Ts = -38°C

the rate of energy loss by radiation = ?

Now, using Stefan-Boltzmann law;

P = σeA [ T⁴ - Ts⁴ ]

Stefan's constant σ = 5.67 × 10⁻⁸

so we substitute

P = 5.67 × 10⁻⁸ × 0.97 ×  0.56  [ (-22 + 273 k)⁴ - (-38 + 273 k )⁴]

= 3.079944 × 10⁻⁸ [ 919325376]

=  28.31 Watt

the rate of energy loss by radiation is 28.31 Watt