Naked Science Forum
General Science => General Science => Topic started by: koundinya75 on 12/04/2013 09:04:35
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I was reading through some of discussions related to cold and heat and I got confused in understanding if cold really exists? Till now I consider it as relative biological factor and Heat is the one which sources the energy.
But people discuss that cold can be one of source of energy. But what I know is variation in temperatures could impact the surroundings and result is heat energy.
Can you share some knowledge in this to understand if cold really exists?
Regards
Koundinya
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Cold is the absence of heat. You get usable energy from temperature differentials. I don't know of cold as a source of energy - remember one definition of temperature is directly related to the average kinetic energy of the constituent particles; I don't see how a system with average lower kinetic energy could be seen as possessing more energy than a similar one with higher kinetic energy
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But what I know is variation in temperatures could impact the surroundings and result is heat energy.
As imatfaal has noted; the word cold is only the definition for an absence of heat. And heat is the measureable value resulting from the motion of molecular particles. In common experience, we extract energy from heat by establishing a controlled environment between this motion and ambient temperature. Consider an environment with ambient temp of absolute zero, such a place would have no available heat energy to use.
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Cold you make "cold" do work? For example if ice expands, or other substances contract with cold, could you harness that change in size to do anything useful?
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Cold you make "cold" do work? For example if ice expands, or other substances contract with cold, could you harness that change in size to do anything useful?
The freezing of any liquid is called a phase transition and would not have been possible without the water ice first being melted. The energy is stored within the water when it is melted, and released again when it freezes. However, the act of freezing only allows the energy put there when it was warm to be released.
Conclusion: The loss of heat does not manufacture energy, but it may in some cases release energy already stored there.
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But people discuss that cold can be one of source of energy.
Heat is one form of energy. To claim that the loss of energy is the source of energy is, quite impossible.
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If the entire environment were at a constant uniform temperature of 5000 degrees (in the atmosphere of the Sun, for example), there is an enormous amount of thermal energy around. However, you cannot extract any of it by using a heat engine (http://en.wikipedia.org/wiki/Heat_engine).
However, if a cold environment suddenly became available to you at 0 degrees Celcius (a large iceblock like a comet, for example), then you can generate considerable useful energy using a heat engine.
An energy flow occurs from the hot environment at 5000C to the cold environment at 0C, and you can tap off some of this energy flow for other purposes. The efficiency of a heat engine increases the greater the temperature difference between the hot and cold sink.
The theory of heat engines ignores minor practical considerations like: any physical machine made of familiar solid matter would evaporate into a plasma in an environment at 5000C...