Plasma free energy question

[fonograph]

Dont worry,I dont believe in any free energy pseudo science,as a physics noob I just dont see where the energy comes from in this scenario so it appears as free energy through I am sure it isnt since that is impossible.I was about to ask this on Stackexchange but that site sucks donkey balls,vast majority of my questions go completly ignored for eons,and if someone responds its useless answer... so decided to ask here.

Imagine a electret,wtf is electret you ask? Its just like magnet except instead of magnetic,its electric,and near this p electret is needle electrode connected to high voltage powersupply,the high voltage causes corona discharge,suddenly neutral air becomes charged ions.The ions will be pushed or pulled by the electret.

Now,my question is this,where the hell does that energy come from? The electret pushes/pulls and accelerates the ions,they gain kinetic energy,I dont understand where does this enery come from.

When I was learning about magnets,I read that the energy that magnet gives to object as it push it away is energy you gave when you forced that object to be close to magnet,its kind of like spring.But here,we arent pushing against repulsive force,the atoms just become suddenly ionized in one spot,if what we look for are ions,then its like they pop up into existance out of nowhere.

I am physics noob but I dont see how the electret can do work,its just piece of stationary charge,the high voltage powersupply certainly does work,but that only goes to ionisation,it doesnt explain kinetic energy gained by the ions by the presense of electret.

[T3sl4co1l]

I somehow doubt you'll get a corona pulse from waving a needle around an electret...

Supposing you set up the experiment properly, you'll notice the charge bleeds away almost instantly.  There is energy but not power.

So you have to move the needle to the other side, to get the opposite polarity.  Then either you get another discharge, or you have to discharge it manually then repeat another cycle to get the same polarity pulse as in the first instance.

What have you done, through all of this?  Mechanical work, of course.  The electret is merely polarizing the system, it is not powering it.

Tim

[IanB]

Imagine a electret,wtf is electret you ask? Its just like magnet except instead of magnetic,its electric,and near this p electret is needle electrode connected to high voltage powersupply,the high voltage causes corona discharge,suddenly neutral air becomes charged ions.The ions will be pushed or pulled by the electret.

Now,my question is this,where the hell does that energy come from? The electret pushes/pulls and accelerates the ions,they gain kinetic energy,I dont understand where does this enery come from.

An ion is an air molecule that has had an electron stripped off it. It takes energy to strip an electron off a molecule, since the electron is bound fast and doesn't want to let go. The energy used to create the ions is the source of energy that causes the ions to have potential energy, and later kinetic energy. Just like a heavy weight in a gravitational field, at some point work had to be expended to put the weight where it is, and that work is the source of the kinetic energy of the weight when it falls.

[fonograph]

No,its not,the ionisation energy have nothing to do with the kinetic energy gained by the presence of electret! I already wrote that in my original post,I repeat,the ionisation process energy,be in high voltage pulse to needle electrode or UV photon,does NOT have anything to do with the kinetic energy the ion gains from the electret.

[IanB]

No,its not,the ionisation energy have nothing to do with the kinetic energy gained by the presence of electret! I already wrote that in my original post,I repeat,the ionisation process energy,be in high voltage pulse to needle electrode or UV photon,does NOT have anything to do with the kinetic energy the ion gains from the electret.

If you ask a question and then argue with the person who gives you the correct answer you will learn nothing.

Good luck!

[Brumby]

No,its not,the ionisation energy have nothing to do with the kinetic energy gained by the presence of electret! I already wrote that in my original post

Doesn't mean you're right.


Forget the electret.  It does not represent anything special at all.  It is simply a body with charge.  How it got there is irrelevant.

Just consider it as an experiment in charge attraction/repulsion.

[fonograph]

 But you didnt give correct answer,I asked where does the kinetic energy of ion induced by the presence of electret come from and you claimed it comes from ionisation source,that is not true.

Lets consider a UV photon with just enough energy to eject electron,it does give the electron kinetic energy,yes,but its all energy of that UV photon,if it happens near electret,it will gain aditional kinetic energy that comes from the fact electret is nearby,not from UV photon,so you cant say the energy comes from ionisation source.

Just so you understand how wrong you are,imagine single Caesium atom,its first ionisation energy is 3.9 eV.Its floating in zero gravity vacuum,its positioned on the surface ,between the two electrets. The electrets are charged to 390V ,one is positively charged,other negative,the lonely Caesium atom is on the negative one.

If UV photon with 3.9 eV energy strikes the Caesium,the electron is ejected.It starts to move in the direction of the positive electret,once its reached,it will gain 390 eV worth of kinetic energy.I ask you,where does this energy come from? Its not ioniastion energy thats for sure,since that is only 3.9 eV,two orders of magnitude bellow our final kinetic energy.

[Brumby]

 

None so blind as those who will not see.

[T3sl4co1l]

If UV photon with 3.9 eV energy strikes the Caesium,the electron is ejected.It starts to move in the direction of the positive electret,once its reached,it will gain 390 eV worth of kinetic energy.I ask you,where does this energy come from? Its not ioniastion energy thats for sure,since that is only 3.9 eV,two orders of magnitude bellow our final kinetic energy.

Like I said before:

The work constructing the electric field was consumed during mechanical arrangement of the components.

In turn, in this situation, that work is done on the electron-ion pair.  As a result, energy is consumed: the electron and ion become trapped in the electret surfaces, neutralizing some charge.  The field weakens.

Suppose you continue ionizing atoms in the gap.  With each additional charge, the field drops: 390V at first, then 389.9999..., and so on until the field is consumed.  Once the field is at very low levels (probably more than 3.9V, because of statistics and imperfect vacuum in practice), the current decreases significantly, as some atoms recombine rather than neutralize the charge.

If slightly more energy is applied, so that ionization occurs with some excess energy (as kinetic energy), then the ion and electron will take random paths in the near-zero field, with the result that the field remains balanced: if a field is applied, slightly more of each kind will be attracted to one side or the other.

Ionization, in bulk, is simply free space made slightly conductive.  So it should be no surprise that the system evolves towards a state identical to that of two electrets slapped on either side of a metallic block: the field in the block is zero, current can flow through the block, and layers of charge are concentrated on its surface.

It may be easy to ignore the mechanical work done arranging little hunks of ceramic -- a bumbling human can't sense forces that small.  That does not excuse the fact that work is, and must be, performed, in the process.

Tim

[fonograph]

 Thank you T3sl4co1l

You are wrong with the mechanical energy part,it was bad choice to put two electrets into my example since that does require energy since they attract and it made my example unnecesary complex.There might been just single electret,so no need for energy to fight repulsive,attractive forces of the electrets on themselfs.

That being said,you are absolutely correct on the charge neutralisation of the electret! That is very smart,looking back I dont know why it didnt hit me,the electret contains potential energy that is practicaly consumed by either the electron or positive ion that will land on its surface,thats the source of energy.

[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?   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