(1a). Black body has emissivity value of 1, but in reality, the emissivity of real objects is less than 1. Why?? (1b). The tungsten sphere of 250 mm radius is at a temperature of 31°C . If the power radiated by sphere is 107 W, calculate its emissivity value?

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Chapter1: Temperature And Heat
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(1a). Black body has emissivity value of 1, but in
reality, the emissivity of real objects is less than
1. Why??
(1b). The tungsten sphere of 250 mm radius is
at a temperature of 31°C . If the power radiated
by sphere is 107 W, calculate its emissivity
value?
(1c).lf the same sphere is enclosed in room
whose walls are kept at -11°C, what is the net
flow rate of energy out of the sphere in Watts
(W)
Transcribed Image Text:(1a). Black body has emissivity value of 1, but in reality, the emissivity of real objects is less than 1. Why?? (1b). The tungsten sphere of 250 mm radius is at a temperature of 31°C . If the power radiated by sphere is 107 W, calculate its emissivity value? (1c).lf the same sphere is enclosed in room whose walls are kept at -11°C, what is the net flow rate of energy out of the sphere in Watts (W)
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