Q.8 Calculate the energy radiated in one minute by a perfectly black body of surface area 200 cm\(^2\) when it is maintained at 127ºC.
Best answer
Answer: about 1742 J (\(1.742 \times 10^3\) J)
Given: \(A = 200\) cm\(^2\) \(= 2 \times 10^{-2}\) m\(^2\), \(T = 127 + 273 = 400\) K, \(t = 60\) s, \(\sigma = 5.67 \times 10^{-8}\) W/m\(^2\)K\(^4\).
By the Stefan–Boltzmann law, energy radiated \(Q = \sigma A T^4 t\):
\[T^4 = (400)^4 = 2.56 \times 10^{10}\]\[Q = 5.67 \times 10^{-8} \times 2 \times 10^{-2} \times 2.56 \times 10^{10} \times 60\]\[Q = 29.03 \times 60 \approx 1742 \text{ J}\]Log in or create a free account to answer this question.
