Negative heat capacity and thermal reservoir

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Discussion Overview

The discussion revolves around the concept of negative heat capacity and its implications for thermal equilibrium with a reservoir. Participants explore the behavior of systems with negative heat capacity, particularly how they interact with systems of positive temperature and the nature of entropy in these interactions.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant states that an object with negative heat capacity increases in temperature as it radiates energy and decreases in temperature when it absorbs energy.
  • Another participant proposes that when a negative temperature system is in contact with a positive temperature system, energy transfer occurs from the negative temperature system to the positive temperature system, leading to an increase in entropy.
  • A further contribution questions whether a system that is not at equilibrium moves toward or away from equilibrium, suggesting a consideration of the dynamics involved.
  • A later reply indicates that the initial question has been resolved for the participant, but does not elaborate on the specifics of that resolution.

Areas of Agreement / Disagreement

Participants express differing views on the implications of negative heat capacity and its relationship to thermal equilibrium, with no clear consensus reached on the nature of these interactions.

Contextual Notes

The discussion does not resolve the underlying assumptions about the definitions of temperature and equilibrium, nor does it clarify the conditions under which these systems operate.

Afonso Campos
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Say you have an object with a negative heat capacity. This means that the object increases in temperature as it radiates energy and decreases in temperature as it absorbs energy.

I don't understand why this object cannot be in thermal equilbrium with a reservoir.

Any help would be greatly appreciated.
 
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If it is contact with something with positive energy, the negative temperature system will transfer energy to the positive temperature system. The entropy always increases as long as the sign of the temperature is different - but thermal equilibrium is the state of maximal entropy.
 
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Another way to look at what mfb said is suppose you aren't at equilibrium. Does the system move toward it or away from it?
 
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Thank you. I understand it now.
 

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