A metal sphere of surface area 0.0225 m² is in an evacuated enclosure – McqOptions

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1.	A metal sphere of surface area 0.0225 m² is in an evacuated enclosure whose walls are held at a very low temperature. Electric current is passed through resistors imbedded in the sphere causing electrical energy to be dissipated at the rate of 75 W. If the sphere surfaces temperature is measured to be 560 K, while in steady state, calculate emissivity of the sphere surface
A.	0.498
B.	0.598
C.	0.698
D.	0.798
Answer» C. 0.698

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