Out of curiosity, is it theoretically possible to extract electrons from metals, perhaps through the administration of strong magnetic fields? If so, could this, hypothetically, be used as an energy source, or would whatever energy it would yield be equal to the energy it would cost?

 

I do realize that it would be impossible to gain a net energy from the electromagnetic force of the electrons, since whatever energy that might produce would be exactly equal to the energy it would take to extract the electrons from the metal. Metals are, after all, generally electrically neutral.

 

What I was wondering, however, was rather if it would be possible to use the kinetic energy of the electrons. I was thinking of metals because part of the electrons are in the conduction bands instead of in the valence bands; it's these that, in my hypothesis, I was thinking of extracting.

you could do it with a magnetic field in theory. but the magnetic field needs to be tremendously huge. on a scale so far only observed around neutron stars and pulsars.

 

you'd have to put in many many many many many orders of magnitude more energy in than you'd possibly be able to get out of it so using it to store energy is a crap idea.

One way is called a capacitor. You use an electric field to move electrons from one piece of metal to another.

 

Another way is thermionic emission — you"boil" electrons off of a metal, and send them somewhere with an electric field. Useful in cathode-ray tubes.

The photoelectric effect ? Electrons are emitted after the absorption of photons.

You could, one way or the other, remove electrons from metals. But soon you'd see the metal fall apart, since the binding electrons are those you'd be shooting away. This would also be an inefficient way of 'extracting' energy, since the kinetic energy imposed on the electrons would originate in the field you used to extract them. It would get progressively harder to get the negatively charged electrons to leave the increasingly positively charged metal. Also, I can't see how a magnetic field would be useful, since it, to my knowledge, only propels already moving charges in circles. The field of an incredibly large positive charge might be suited for the purpose.

 

All of this is not at all practical, and not even close to useful, unfortunately.