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Plasma free energy question

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T3sl4co1l:
I think you will find, ultimately, I am not wrong on the other point, either; it takes work, for instance, to prepare the surface of the electret so that its external field is not balanced by nuisance charges that have gotten trapped there. :)

Example: ionizing atoms (with little excess kinetic energy) say near the side of an electret, will cause charge separation and the charges will glomp onto the sides, and then faces, and then far side, of the element (kind of being sprayed with charges, so, the process will go rather slowly as there is a small probability of charges wrapping around to the far side, just as with electroplating, or, a bit better than paint spraying, which is uncharged).  Once this has been done, the electret kind of... isn't, anymore, is it? :P  So you need to apply an excess electric field, to suck out those added charges, or brush it past a pair of electrodes which are so charged; and in doing so, work has again been performed. ;)

Tim

fonograph:
I am not sure if I understand you correctly

What do you mean by "prepare surface of electret" ? I dont see need to prepare anything,if you mean creating the electret then that does indeed need energy,and that is the energy that will accelerate the ion/electron,that is the energy this entire question is about and you was first to correctly identify it.

I dont know what "nuisance charges" you mean,if you mean the charges that electret will attract after atoms have been ionized in front of it,then I completly agree,you would have to charge it again to counter the neutralising charged particles that accumulated on its surface.

But my example was just single atom being ionised,thats not enough to neutralise the electret,in my example the electret is "fresh",no nuisance charges on its surface.

The example you gave in your last post I agree,its longer version of what you already stated before,if atoms gets ionized in front of electret,either the  ion or electron will stick to electret,its potential energy gets consumed,so the kinetic energy comes from electret,no need to repeat that,I already  understood it from your earlier post.

T3sl4co1l:
Good. :)

By "nuisance charges", I mean anything that might've stuck to the object between manufacture and test.  This could be triboelectric charges (due to handling), ambient dust, ambient ionization (including cosmic rays), etc.

Incidentally, since the field inside the material is still present (assuming the charges are not able to move -- i.e., the material is an excellent insulator), bulk properties of the material will still play out as intended.  So, an electret need not have an apparent external field, but can still exhibit (prebiased) electrostriction, for example.  Which, of course, is what that type of microphone capsule is all about -- there's no significant voltage in circuit, that's been long since shorted out; but the internal field remains, and generates a small charge (and thus voltage) in response to mechanical deformation.

So, yeah, for the case of just one atom being ionized -- work is done, not much since we're talking atoms and electrons, but what little work is done, ultimately comes from whatever preparation was done setting up the system. :)

Tim

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