Understanding Energy Transfer: Thermodynamics in an Insulated Box Scenario

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    Thermodynamics
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Discussion Overview

The discussion revolves around the thermodynamics of energy transfer in an insulated box containing a refrigerator, particularly focusing on the implications of energy input and its effects on temperature. Participants explore concepts related to heat transfer, laser cooling, and the behavior of systems when energy is added.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions whether adding energy to a system always results in an increase in temperature, using the scenario of an insulated box with an open refrigerator as an example.
  • Another participant asserts that adding heat energy or converting electrical energy to heat will always cause the system to heat up, framing this as a definition of "heating up."
  • A different participant points out that in laser cooling, energy is pumped into the system, yet the temperature decreases, suggesting a contradiction to the previous claim.
  • One participant explains that in laser cooling, energy is removed from the atoms as the laser light is scattered, which leads to cooling rather than heating.
  • Another participant draws a connection between the energy dynamics in laser cooling and the Raman effect, questioning if they are similar processes.
  • A later reply suggests that if the laser cooling occurs in an opaque box, the photons would not escape, leading to an increase in temperature inside the box.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between energy input and temperature change, with some asserting that energy input always leads to heating, while others highlight exceptions such as laser cooling. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants do not fully explore the assumptions behind energy transfer in different contexts, such as the specific mechanisms of laser cooling or the definitions of heat and energy in thermodynamic terms. The implications of energy conservation and transfer in closed systems are also not fully addressed.

cragar
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I once was asked a question about this scenario.
Let's say we have an insulated box with a refrigerator in it.
Now the fridge is plugged in from outside. The box is perfectly insulated.
The door of the fridge is open. What happens to the temperate inside the box.
their is air in the fridge. I was told that the temperature of the box will go up because we are pumping energy into it.
But then I thought of laser cooling. When laser cooling happens we shoot photons into
a cloud of atoms and they Doppler shift the light an absorb them and slow down.
We pumped energy into that system and it cooled down.
Is it always true that if I pump energy into a system that it will heat up.
 
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Yes, it is always true that if you pump heat energy in (or input electrical energy and immediately convert it to heat), it will heat up. That's basically the definition of "heat up".
 
ok but in laser cooling we pump in energy and it cools down.
 
If you cool something, something else must heat up. Laser cooling is mostly used to cool at atom level. I don't find it plausible that this is some kind of optical trapping of the atoms - forcing them to stop viberating. Laser cooling is however mostly used in quantum physics so I can't help you further regarding what heats up if the atoms cools down. At least the laser equipment itself heats up - that for sure :-)

Vidar
 
In laser cooling, the laser light gets scattered and leaves the system with higher energy than the light that entered. So there is no net pumping of energy but energy removal.
 
so the light gets absorbed and then remitted with more energy so it took energy away from the atom. is this similar to the Raman effect.
 
If you ran the laser cooler in an opaque box, where the photons could not leave,
the inside of the box would heat up as well.
 

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