How Does a Sphere Exchange Thermal Radiation in Different Temperatures?

AI Thread Summary
A sphere with a radius of 0.5m, temperature of 27°C, and emissivity of 0.85 is analyzed for its thermal radiation exchange in an environment at 77°C. The emission of thermal radiation should be calculated using the sphere's temperature, while the absorption should use the environment's temperature. The net rate of energy exchange is determined by subtracting the emission from the absorption. The relevant equation for calculating power is P = d(ε)(A)(T^4), where A is the surface area and T is the temperature in Kelvin. Understanding these principles is crucial for solving the problem effectively.
bmb2009
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Homework Statement


A sphere of radius .5m, temperature of 27 deg C, and emissivity = .85 is located in an environment of temperature 77 deg C. At what rate does the sphere (a)emit and (b)absorb thermal radiation? (c)What's the sphere's net rate of energy exchange?



Homework Equations





The Attempt at a Solution



(a). I know I must use the equation P = d(ε)(A)(T^4) where d = stefan-Boltz constant, ε= emissivity, A=surface area, T=temperature...but which temperature is it? I believe I should use the Sphere's temp for the emission quantity and the temp of the enviorment for the absorption radiation quantity. Is that correct?

(c) I haven't been given an equation for net rate of energy exchange but wouldn't it just be absorption - emission ?

Thanks for the help!
 
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Yes, that all looks right to me. Degrees K, of course.
 
bmb2009 said:

Homework Statement


a sphere of radius .5m, temperature of 27 deg c, and emissivity = .85 is located in an environment of temperature 77 deg c. At what rate does the sphere (a)emit and (b)absorb thermal radiation? (c)what's the sphere's net rate of energy exchange?



Homework Equations





The Attempt at a Solution



(a). I know i must use the equation p = d(ε)(a)(t^4) where d = stefan-boltz constant, ε= emissivity, a=surface area, t=temperature...but which temperature is it? I believe i should use the sphere's temp for the emission quantity and the temp of the enviorment for the absorption radiation quantity. Is that correct?

(c) i haven't been given an equation for net rate of energy exchange but wouldn't it just be absorption - emission ?

Thanks for the help!

a-ok.
 

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