- #1
JC2000
- 186
- 16
- TL;DR Summary
- 1.My book tells me that given ##T_{surroundings}##, and ##T## of the object radiating heat, the law is expressed as ##H = \sigma A (T^4 - T^4_{surroundings})##.
2. Relating Newton's Law of Cooling, Conduction, and Stefan-Boltzmann Law
3. Is emissivity the same as Stefan's constant or is it ## e * \sigma## where ##e## varies, depending on the material?
1.If so what would the law mean if ##T_{surroundings}>T##?
2. Stefan-Boltzmann Law is formulated as ##H = A\sigma T^4## where ##H## is the energy emitted per unit time, ##A## is the area of the object, ##T## is the absolute temperature of the object and (3.) I am unclear about whether ##\sigma## represents emissivity or ##e*\sigma## represents Stefan's constant.
My book also defines Conduction (as the time rate of heat flow for a given temperature difference), as ##H = kA \frac {T_c - T_d}{L}## where ##H## is the rate of flow of heat (heat current), ##A## is the area of cross-section and ##L## is the length between the two points being considered, ##T_c - T_d## the temperature difference between the points.
Newton's Law of Cooling is stated as a special case of Stefan-Boltzmann Law where the temperature difference is very small and is formulated as ##\frac {dQ}{dt} = k(T_2 - T_1)##.
I feel that the three must be somehow interrelated, am I correct in assuming this? If so, how?
3. Lastly is emissivity the same as Stefan's constant or is it ## e * \sigma## where ##e## varies, depending on the material?
Thank you!
2. Stefan-Boltzmann Law is formulated as ##H = A\sigma T^4## where ##H## is the energy emitted per unit time, ##A## is the area of the object, ##T## is the absolute temperature of the object and (3.) I am unclear about whether ##\sigma## represents emissivity or ##e*\sigma## represents Stefan's constant.
My book also defines Conduction (as the time rate of heat flow for a given temperature difference), as ##H = kA \frac {T_c - T_d}{L}## where ##H## is the rate of flow of heat (heat current), ##A## is the area of cross-section and ##L## is the length between the two points being considered, ##T_c - T_d## the temperature difference between the points.
Newton's Law of Cooling is stated as a special case of Stefan-Boltzmann Law where the temperature difference is very small and is formulated as ##\frac {dQ}{dt} = k(T_2 - T_1)##.
I feel that the three must be somehow interrelated, am I correct in assuming this? If so, how?
3. Lastly is emissivity the same as Stefan's constant or is it ## e * \sigma## where ##e## varies, depending on the material?
Thank you!
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