Interaction between blackbodies in relation to the second law

In summary, the conversation discusses the behavior of two blackbodies, B_1 and B_2, with different temperatures, T_1 and T_2, in thermal contact through radiation exchange. The second law of thermodynamics allows for B_2 to give energy to B_1, but the net energy exchange will always involve B_1 giving more energy to B_2. This can be represented by the equation dQ\Big( \frac{1}{T_2} - \frac{1}{T_1}\Big)=dQ\Big( \frac{T_1-T_2}{T_1T_2}\Big)>0, where dQ is the net heat and the positive direction is
  • #1
Shunyata
3
0
I am trying to understand the behavior of blackbodies in interaction with each other.

Conditions as follows.

[itex] 1)[/itex] There are two blackbodies, say [itex]B_1[/itex] and [itex]B_2[/itex], with corresponding temperature [itex]T_1[/itex] and [itex]T_2[/itex].

[itex]2)[/itex] Initially [itex]T_1>T_2[/itex].

[itex]3)[/itex] [itex]B_1[/itex] and [itex]B_2[/itex] have thermal contact only through radiation exchange.

And finally my question,

Can [itex]B_2[/itex] give energy to [itex]B_1[/itex] or is this prevented by the second law?
 
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  • #2
Sure it can. In fact, it always will be. However, B1 will always be giving more energy to B2 than the reciprocal effect, so the net energy exchange will always involve B1 giving energy to B2.
 
  • #3
Is it as simple as

[itex]dQ\Big( \frac{1}{T_2} - \frac{1}{T_1}\Big)=dQ\Big( \frac{T_1-T_2}{T_1T_2}\Big)>0,[/itex]

if [itex]dQ=dQ_1 - dQ_2[/itex] is the net-heat where positive direction is from [itex]B_1[/itex] to [itex]B_2[/itex] and [itex]dQ_1>dQ_2[/itex]?
 

1. What is the second law of thermodynamics and how does it relate to the interaction between blackbodies?

The second law of thermodynamics states that in any isolated system, the total entropy will always increase over time. This means that energy will naturally flow from hotter objects to colder objects, and that all energy transfers will result in some energy being lost as heat. In relation to blackbodies, this means that when two blackbodies interact, the hotter one will transfer energy to the colder one until they reach thermal equilibrium.

2. How do blackbodies interact with each other?

Blackbodies interact through the process of thermal radiation. This occurs when the atoms or molecules within a blackbody absorb energy from an external source and emit it as electromagnetic radiation. This radiation can then be absorbed by another blackbody and cause its temperature to rise.

3. Can blackbodies transfer energy without interacting?

No, blackbodies can only transfer energy through thermal radiation by interacting with other objects. This is because blackbodies are perfect absorbers and emitters of radiation, meaning they cannot reflect or transmit radiation like other objects.

4. How does the interaction between blackbodies follow the second law of thermodynamics?

The interaction between blackbodies follows the second law of thermodynamics because it results in an increase in entropy. As energy is transferred from the hotter blackbody to the colder one, some of it is lost as heat, increasing the overall entropy of the system. This process will continue until both blackbodies reach thermal equilibrium, at which point there is no more energy transfer and the system remains in a state of maximum entropy.

5. Are there any exceptions to the second law of thermodynamics in relation to blackbody interaction?

There are no known exceptions to the second law of thermodynamics in relation to blackbody interaction. However, there are some theoretical scenarios in which it may appear that energy is spontaneously transferring from a colder object to a hotter one, violating the second law. However, in these cases, there are other factors at play, such as the work done by an external force, that explain the apparent violation of the law.

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