A metal ball of surface area `200 cm^(2)` and temperature `527^(@)C` is surrounded by a vessel at `27^(@)C` . If the emissivity of the metal is 0.4, then the rate of loss of heat from the ball is `(sigma = 5.67 xx10^(-8)J//m^(2)-s-k^(4))`

Options

A. 108 joule
B. 168 joule
C. 186 joule
D. 192 joule

Answer

C

Explanation

As we use `P=Aesigma(T^(4)-T_(0)^(4))`
`implies P=(200xx10^(-4))xx(0.4)xx(5.67xx10^(-8))[(527+273)^(4)-(27+273)^(4)]`
`implies P=(4.54xx10^(-10))xx(4.096xx10^(11)-8.1xx10^(9))`
`implies P=4.54xx10^(-10)xx4.015xx10^(11)`
`impliesP=182.3Japprox186J`