Question

A body heated to 1000k, uses surface area 10cm². It radiates 340.2 J energy per minute. So emissivity is ........ . (Ï = 5.67 à 10â»â¸ W mâ»Â² Kâ»â´) (A) 0.1 (B) 0.02 (C) 0.01 (D) 0.2

Answer 1

Answer:

option A 0.1 is correct

Answer 2

Answer:

Emissivity = 0.1

Explanation:

As per the question we have been provided,

Temperature = 1000 k

Area (A) = 10 cm²

Heat energy (Q) = 340.2 J

Time (t) = 1 minute = 60 sec

Formula used:

$Emissivity \ (e) = \frac{Q}{\sigma AT^{4} t}$

where,

σ = 5.67 × 10⁻⁸ W⋅m⁻²⋅K⁻⁴

Now put all the given data in the above equation, we have

$Emissivity \ (e) = \frac{340.2}{5.67 \times 10^{-8} 10 \times 10^{-4}(1000)^{4} 60}$

e = 0.1

Hence, the value of emissivity = 0.1.