# Energy conservation law

## Main Question or Discussion Point

Hello,

I nowhere find general form of energy conservation law, but in one book i found this

$$(*)\hspace{1cm}E=E_{in}-E_{out}+E_{generated}$$

where E(in) is energy flow into system, E(out) is energy flow out of system and E(generated) is energy generated. It was in sense of heat conservation. Can I use this form of heat conservation law? Or is it true, when I say, (*) is energy conservation law?

## Answers and Replies

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Jewett Jr. has actually presented a somewhat "global energy conservation equation" in Energy and the Confused Student IV: A global approach to energy (Phys. Teach. 46, 210 (2008)). You can access it here: http://dx.doi.org/10.1119/1.2895670

It is a simple concept, it does not require mathematics to understand. What you wrote up there looks like the energy conservation principle applied to a control volume in some particular case.

If you are just looking for a formula to plug and chug at, you won't find it. Not that it would be useful anyways.