Acircular grill of diameter 0.25 m has an emissivity of 0.8. if the surface temperature is maintained at 150°c, determine the required electrical power when the room air and surroundings are at 30°c.

the required electrical power when the room air and surroundings are at 30°C.= 52.51822 Watt

Explanation:

Power required to maintain the surface temperature at 150°C from 20°C

P= εσA(T^4-t^4)

P= power in watt

ε= emissivity

A=  area of surface

T= 150°C= 423 K

t= 20°C= 303K

/sigma= 5.67×10^{-8} watt/m^2K^4

putting vales we get

P=52.51822 Watt

the required electrical power when the room air and surroundings are at 30°C.= 52.51822 Watt

the doppler effect is used by weather forecasters to measure 

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