Question

How many watt of energy is required to keep a black body, in the form of a cube of side $1$ cm, at $2000K$? (Surrounding temperature is ${27}^{0}C$ and $\sigma =5.67\times {10}^{-8}W{m}^{-2}{K}^{-4}$)

• A. 444 W
• B. 544 W
• C. 644 W
• D. None of the above

Answer 1

Answer: (B)

544 W

Using the formula: $E=\sigma (T^4-T_o^4)$

where,

$E=$ Flux

$\sigma =5.67\times {10}^{-8}W{m}^{-2}{K}^{-4}$

$T=2000K$

$T_o$ = $300K$

Total surface area of cube $=6(0.01{)}^2$

Energy required $=E\times TSA=544W$

σ=5.67×10−5Wm−2K−4