> You really think or say that a device burning a dvd disc or 
> playing music is using the energy for only to generate heat ? 
> There occures some heat but it is obvious that the amount of 
> energy used by the device is not equal to the heat it 
> generated.I do not even mention about piezo materials.
> 
> Yigit


No, I said it ends up as heat eventually.

The spinning disc has a certain about of kinetic energy.  Nothing last
forever, friction will eventually make it stop, and friction means heat.

Pick up a rock, and put it on the shelf.  (It takes you a certain amount of
energy to lift it, but ignore that.)

The rock has potential energy sitting there.  Now push it off.

On it's way down, there is friction from the air.  This slows the rock down,
and heats up the air.

The rock hits the floor.  The rock or the floor may deform, bending means
heat is created.

A noise is created, which is just air moving.  Air banging into more air
creates heat.

It's all heat eventually.

In theory, all that heat could be collected and used to lift the rock back
up, but it doesn't work that way.

Tony

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