# Conservation of energy?

Discussion in 'Physics' started by Niles, Apr 7, 2009.

1. ### Niles Thread Starter Active Member

Nov 23, 2008
56
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Hi all.

Lets look at the following scenario: We have an object called A which is kept at 300 K at all times (e.g. a hot plate). Now we have an object B, which is initially 200 K (e.g. a frying pan), and object A and B are now moved together, so they touch eachother.

Of course, object B will now be 300 K as well, and object A is still 300 K.

When I explain this to someone, I would just say that it is intuitively clear that this is how it must be. But can one explain this using conservation of energy, or some other physical law?

I thought about using the first law of thermodynamics: Q = U, but how does one explain that the heat provided by A will make the internal energy of B rise enough, so that the temperature of B is also 300 K?

- Niles.

Last edited: Apr 7, 2009

May 16, 2005
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3. ### Niles Thread Starter Active Member

Nov 23, 2008
56
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Oh, the heat equation is of course also a possible explanation.

Do you know of any others?

4. ### fanta_hanu New Member

Mar 9, 2009
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it can be explained using STEADY STATE ENERGY EQUATION....

5. ### Ratch New Member

Mar 20, 2007
1,068
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Niles,

It appears to be an event called conduction.

But not immediately. It will take time for the heat energy to propagate throughout the frying pan to bring it up to the temperature of the hot plate.

You are right. It is intuitive. It is just heat energy moving from one object to another via conduction. Same with heating water in a pot. Ever hear of Fourier's Law of Conduction? http://www.taftan.com/thermodynamics/FOURIER.HTM

I don't see why there should be doubt or confusion. Heat transfer through conduction happens constantly everywhere.

Ratch

Last edited: Apr 20, 2009
6. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515
You are right to wonder as the First and Second laws of Thermodynamics cannot be derived from more fundamental physical theories. They have just never been observed to be disobeyed.

It has been necessary to introduce something called the Zeroth Law of Thermodynamics to help overcome this.

http://en.wikipedia.org/wiki/Zeroth_law_of_thermodynamics