Dissipated Energy: Where does it go?? Watch

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MorningElegance
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For ages now I have wondered where dissipated energy goes...

Energy can't be created or destroyed, so how come almost every time there's a net loss in energy someone uses the 'dissipated energy through heat or sound' excuse!

I am only an AS/A Level Physics student, and I am no expert (obviously), so sorry if this sounds unbelievably stupid, but can someone please explain this to me?
I would be eternally grateful
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Scipio90
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If it's dissipated as heat or sound, it goes into heat or sound...
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MorningElegance
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(Original post by Scipio90)
If it's dissipated as heat or sound, it goes into heat or sound...
But where does that energy go afterwards? the sound doesn't last forever :confused:
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TheSadReaper
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Heat or sound which is a waste because you want it for a different purpose.

So like a light-bulb, it gets crazy hot, this shouldn't be the case its purpose is to emit light, not to be a radiator. We call this energy being wasted.
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radiated yoghurt
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North Korea
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Oh my Ms. Coffey
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Toothfairy takes it.
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MorningElegance
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(Original post by TheSadReaper)
Heat or sound which is a waste because you want it for a different purpose.

So like a light-bulb, it gets crazy hot, this shouldn't be the case its purpose is to emit light, not to be a radiator. We call this energy being wasted.
Thanks, but what I meant was where does this 'wasted energy' end up being transferred to? i know heat will warm up the environment around it, but for example, if energy continues being dissipated over time, what is all this 'wasted energy' doing? What would transfer it out of its dissipated state? Maybe I'm just confused about the definition of 'dissipated energy'...
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Bunkd
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(Original post by MorningElegance)
Thanks, but what I meant was where does this 'wasted energy' end up being transferred to? i know heat will warm up the environment around it, but for example, if energy continues being dissipated over time, what is all this 'wasted energy' doing? What would transfer it out of its dissipated state? Maybe I'm just confused about the definition of 'dissipated energy'...
Well sound is just vibration of molecules, so in a sense its molecular kinetic energy. You may also know that heat is simply molecular kinetic energy. These are both transfered through collisions between particles.

Alternatively (though I don't know the mechanism), the heat is radiated via infra-red to a colder place in the Universe (thermodynamic entropy)
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MorningElegance
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(Original post by Bunkd)
Well sound is just vibration of molecules, so in a sense its molecular kinetic energy. You may also know that heat is simply molecular kinetic energy. These are both transfered through collisions between particles.

Alternatively (though I don't know the mechanism), the heat is radiated via infra-red to a colder place in the Universe (thermodynamic entropy)
but if dissipation is happening all the time, shouldn't this mean molecular kinetic energy is increasing? maybe the thermodynamic entropy explains that by transferring it to other places in the universe, if i understand that correctly!
and THANKS
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F1 fanatic
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(Original post by MorningElegance)
but if dissipation is happening all the time, shouldn't this mean molecular kinetic energy is increasing? maybe the thermodynamic entropy explains that by transferring it to other places in the universe, if i understand that correctly!
and THANKS
As you say, entropy always increases and the universe is becoming more and more disordered. Eventually the entire universe will equilibrate to the same (very cold!) temperature as energy will be transferred equally between all matter. Of course the timescale for that is extremely long! The energy has not gone anywhere, but by "dissipating" it ceases to be useful.
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Bunkd
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(Original post by MorningElegance)
but if dissipation is happening all the time, shouldn't this mean molecular kinetic energy is increasing? maybe the thermodynamic entropy explains that by transferring it to other places in the universe, if i understand that correctly!
and THANKS
As for your first point, no; since in every intermolecular 'collision', energy is gained by one molecule but lost by other; the total energy is the same (consider conservation of momentum laws).

Thermodynamic entropy does transfer this energy to other (colder) places in the Universe, as explained by the poster below my last post. The reason we havent lost all our heat is due to the fact that more is produced continuously by nuclear decay reations within the Earth and of course the Sun's radiation, as well as the effect of (in particular C02), which absorbs the infra-red radiation before it leaves our atmosphere due to its natural frequency of oscillation matching the frequency of IR radiation - meaing the heat radiation energy is converted back into molecular kinetic energy within our atmospher. Hence, anyone who denies the greenhouse effect is basically a philistine and/or moron. (Global Warming is a slightly different matter however.)
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MorningElegance
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#12
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Thanks to everyone
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lizzieromeo2
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#13
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I don't get it were dose the energy go if it cant be destroyed
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Stonebridge
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#14
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This is an old thread from 2010 as is now closed.
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