Question 656: Thermodynamics & KTG

Question

A rectangular black body of temperature $127^{\circ} \mathrm{C}$ has surface area $4 \mathrm{~cm} 	imes 2 \mathrm{~cm}$ and rate of radiation is E . If its temperature is increased by $400^{\circ} \mathrm{C}$ and surface area is reduced to half of the initial value then the rate of radiation is

Accepted Answer

$$ \begin{aligned} &	ext { Energy radiated from a black body, }\ &\begin{aligned} & \mathrm{Q}={\mathrm{A} \sigma \mathrm{~T}^4 \mathrm{t}} \ 	herefore & \frac{\mathrm{Q}_2}{\mathrm{Q}_1}=\frac{\mathrm{A}_2}{\mathrm{~A}_1} 	imes\left(\frac{\mathrm{T}_2}{\mathrm{~T}_1}ight)^4=\frac{1}{2} 	imes\left(\frac{800}{400}ight)^4=8 \ 	herefore & \mathrm{Q}_2=8 \mathrm{E} \end{aligned} \end{aligned} $$

Answer

4 E

Answer

E

Answer

2 E

Answer

16 E

Thermodynamics & KTG

A rectangular black body of temperature 127^{\circ} \mathrm{C} has surface area 4 \mathrm{~cm} \times 2 \mathrm{~cm} and rate of radiation is E . If its temperature is increased by 400^{\circ} \mathrm{C} and surface area is reduced to half of the initial value then the rate of radiation is

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