Question

A black body at 227°C radiates heat at the rate of 7 cals/cm²s. At a temperature of 727°C, the rate of heat radiated in the same units will be

(a) 50

(b) 112

(c) 80

(d) 60

Answer 1

Correct option (b) 112

Explanation:

Rate of heat radiated at (227+ 273) K = 7 cals/(cm²s)

Answer 2

Option (b) is correct.

Explanation

By Stefan Boltzman heat radiation of black body we know that rate of heat radiated from the black body is proportional to the absolute temperature of it's surface.

So P2/P1=T₂​​​​​^4/T₁​​​​​^4

Hence 

P2=7×(727+273)^4/(227+273)^4Cal's/cm^2s

=>P2=7×2^4=112cals/cm^2s

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