Question

The temperature of perfect black body is $727{}^\circ C$ and its area is $0.1\,{{m}^{2}}$ . If Stefans constant is $5.67\text{ }watt/{{m}^{2}}s{{K}^{-4}},$ then heat radiated by it in 1 minute is:

• A. 8100 cal
• B. 81000 cal
• C. 810 cal
• D. 81 cal

Answer 1

Answer: (B)

81000 cal

Answer 2

$Q=A\sigma t{{T}^{4}}$ $=\frac{0.1\times 5.67\times {{10}^{-8}}\times 60\times {{(1000)}^{4}}}{4.2}\text{cal}$ $=81000\,cal$