Question

A blackbody with initial temperature of 300 °C is allowed to cool inside an evacuated enclosure surrounded by melting ice at the rate of 0.35 °C/second. If the mass, specific heat and surface area of the body are 32 grams, 0.10 cal/g °C and 8 cm² respectively, calculate Stefan’s constant. (Take J = 4200 j/kcal.)

Answer 1

Data : T = 273 + 300 = 573 K, T₀ = 273 K,

\(\frac{dQ}{dt}\) = 0.35 °C/s = 0.35 K/s, at

M = 32 g = 32 × 10^-3 kg, A = 8 cm² = 8 × 10^-4

m²C = 0.10 cal/g.°C = 0.10 kcal/kg.K = 420 j/kg.K

since J = 4200 J/kcal

Stefan's constant, σ = 5.754 x 10^-8 W/m².k⁴