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Heat Transfer - Engineering

Q1:

Pick out the wrong statement:

A With change in temperature, the radiant energy emitted by a black body remains unchanged.

B Absorptivity of a body approaches unity in case of diffuse reflection.

C Absorptivity of a perfectly black body is unity.

D Value of Stefan-Boltzman constant is 4.876 x 10-8 KCal/m2.hr.°K4.

ANS:A - With change in temperature, the radiant energy emitted by a black body remains unchanged.

The wrong statement among the options is: "Value of Stefan-Boltzmann constant is 4.876 x 10-8 KCal/m2.hr.°K4." The correct value of the Stefan-Boltzmann constant is approximately 5.67×10−85.67×10−8 W/m²K⁴, not 4.876 x 10-8 KCal/m2.hr.°K4. So, the statement "Value of Stefan-Boltzman constant is 4.876 x 10-8 KCal/m2.hr.°K4" is incorrect.