A theoretical question about mater/antimatter and capacitors

[rgawron]

Let's assume that the experiment is done in a vacuum and there's a circuit as in attachment. Values of voltage/resistance/capacitance are insignificant.

Assume that the right terminals of capacitors and the wire that connect them is made from antimatter, all else is made from regular matter.

My question is, would the voltage observed on resistor be the same as with above terminals/wires made from regular matter?

[RoGeorge]

That's an interesting question, such a can of worms!   

My guess is that it will make no difference if the right side of the plates + the wire between them is made of antimatter.  The reasoning is that the laws of nature, here the Maxwell's equations, does not change.  They remain valid even for no matter at all, in vacuum, so I guess it doesn't matter the charge of elementary antiparticles.

[Domagoj T]

Wouldn't the electrons, as soon as they pass from left side to the right, slam into the positrons of the antimatter side of the capacitor, leading to annihilation?

[magic]

I suppose that if you push electrons into C1 then they will attract positrons to the other side of C1 and suck them out of C2, which will repel electrons from C2 and send them back to your voltage source. So probably everything will behave normally and electric fields and voltages will be same as usual, because one elementary charge is one elementary charge, regardless of what charge carrier brought it in.

Provided that you can prevent the electrons and positrons from jumping the gap and annihilating
If not, then you will perhaps get a rectifier or something like that

[RoGeorge]

Wouldn't the electrons, as soon as they pass from left side to the right, slam into the positrons of the antimatter side of the capacitor, leading to annihilation?

In a normal capacitor the electrons does not pass from one plate to another.  They just attract or repel charges from the other plate, without jumping from one plate to another.  Why would they jump between plates in a matter/antimatter capacitor?

[magic]

Why not?

Back in the day people built electronics out of vacuum capacitors which leaked electrons like crazy. It seems just a matter of voltage and temperature

[RoGeorge]

In vacuum tubes, the electrons are first "ejected" out of the cathode's metal because of the heating, then once they are floating they are accelerated by the electric field produced by the anode's positive potential.  By themselves, electrons like to stay close to the protons, so they won't leave the metal plates unless they are forced to leave.

[unitedatoms]

That reminds me about Robert Wood (physicist) describing theoretical experiment. Two boys hold plates close comprising a capacitor. The plates are charged. Then boys are commanded to walk backwards. According to law of energy conservation and work over time of applied attracting force and dielectric strength of air or vacuum and capacitance formula of inverse square of gap distance (am I remember correctly), the prediction is that there is a breaking point when plates will catastrophically discharge and kill the boys.

[RoGeorge]

I'm pretty sure this doesn't happen (the discharge) or else everybody will be dead by now, airplanes won't fly, and so on.

[unitedatoms]

That is not my claim, but my imperfect memory of biographical book. The air is full of ions, so the leaks allow the discharge to happen slowly. Someone (second year EE Major may be) should redo the math and tell what should be predicted. I am too busy with undecorating the Christmas tree and starting to wait for next Christmas

[Mechatrommer]

here what happens...


in short, nothing happens because some of the matter plate anihilates with the antimatter plate, and the energy produced burn down the rest of resistor, battery and the operator. leaving world in great recession after spending lots just to produce the antimatter plate and wire in the first place. even if it does something happen, electromagnetic from the antimatter trap tank will deviate electrons matter to unknown or irrelevant direction. and in both cases. no practical or usefull application. let the men do their job...

[RoGeorge]

Any equation without explaining the terms can mean anything.
Care to explain it, or at least link where from did you took that?

The matter and antimatter plates are separated by vacuum.
How can matter and antimatter annihilate through vacuum?

[Jwillis]

This of course puts aside all laws of physics .
Lets assume that you conquered matter/antimatter annihilation. So you now have an antimatter capacitor charged with positron's. And assume that you developed a way to transfer those positrons to a conventional circuit without causing a massive explosion ,the charge would flow opposite of a conventional capacitor so your polarities would have to be reversed. But you would not achieve anything better than a conventional capacitor.     

[atmfjstc]

Way I see it, as long as you can keep each capacitor's plates from touching each other (you'd have to use vacuum as a dielectric, of course), and not get the thing hot enough to start thermionic emission, everything should work just as in the "all normal matter" case. Electrostatically, a positron being pulled closer is the same as an electron being pushed away. And as someone mentioned before, electrons (or positrons) won't just fly off the metal into space by themselves.

Quite how you would go about keeping the plates separate is the real question, since in a capacitor the plates will attract each other when charged. In a real vacuum capacitor, the plates are secured against the same mechanical assembly, so they ARE touching each other, just not through anything conductive. This is not an option here. One side being made of antimatter pretty much means it must be kept floating in a void vis a vis the other side. For a moment I thought you could stabilize things with a geometry like this one:


-------| |--------------| |------
|          ^antimatter^         |
|                               |
--------(~)---------[R]----------


With all wires being rigid. But this is an unstable equilibrium since the force between the plates increases quadratically. Only way you could keep this system in one piece is by dynamically adjusting the position of one side of the system with some rocket (anti-rocket?) system, or by pushing it with photons. All seems very impractical just to charge a capacitor...

[CatalinaWOW]

You really have to carefully define your problem to get a sensible answer.

Case one.  The left plate has conventional electrons.  The right plate has a similar number of anti-matter electrons (positrons, which have a charge of +1).  From an electric field standpoint this is identical to the conventional case.  You can't talk about ohms law because any current which flows will result in anti-matter and matter coming in contact with large release of energy.  The only way to construct such a capacitor in principal would  be to make a normal matter capacitor and an anti-matter capacitor, and then pull the plates of each apart (either magnetically, or since this is a thought experiment, with tractor beams) and then bring the appropriate matter and anti-matter plates into proximity.  One pair will have a surplus of electrons on one plate and a surplus of positrons on the other.  The other pair will have similar deficiencies.

Case two.  The left plate has conventional electrons.  The right plate has a shortage of positrons.  In terms of shortages and surpluses this is analogous to a conventional capacitor.  This pair can be assembled in manner similar to that used in case one.  In this case the electric field is zero between the plates (assuming the other pair of plates has been moved "infinitely" far away.  But you still can't put a wire between the plates because it again will lead to an explosion.  Even though there will be no large scale electrostatic forces bringing the two types of matter together, at some point in the wire the matter type has to change and that interface would be unstable.

[calzap]

The voltage source, resistors and wires are irrelevant.  With metal plates of matter and antimatter that close, there would quickly be a nuclear explosion. Even without heating, at any temperature above 0 K, there would be occasional electrons or positrons making the journey through the vacuum to the other side or meeting in the middle.  The time lag at usual room temperatures would be very short.  In addition, to thermal excitation, bombarding cosmic rays or radioactive impurities in the plates could excite electrons and positrons into leaving.  The annihilation gamma radiation from electrons and positrons meeting would bombard the plates, interact there, and release more electrons/positrons.  As the lepton interactions become more frequent, the increasing energy release will knock atoms or their nuclei across the gap.  Then the really big energy release starts.  A runaway chain reaction ensues.

Mike in Calfornia

[Mechatrommer]

How can matter and antimatter annihilate through vacuum?

if its that easy? CERN scientists will already have vaccum pendant filled with anti-hydrogen going around.

[atmfjstc]

The voltage source, resistors and wires are irrelevant.  With metal plates of matter and antimatter that close, there would quickly be a nuclear explosion. Even without heating, at any temperature above 0 K, there would be occasional electrons or positrons making the journey through the vacuum to the other side or meeting in the middle.  The time lag at usual room temperatures would be very short.  In addition, to thermal excitation, bombarding cosmic rays or radioactive impurities in the plates could excite electrons and positrons into leaving.  The annihilation gamma radiation from electrons and positrons meeting would bombard the plates, interact there, and release more electrons/positrons.  As the lepton interactions become more frequent, the increasing energy release will knock atoms or their nuclei across the gap.  Then the really big energy release starts.  A runaway chain reaction ensues.

Mike in Calfornia

Not necessarily. Yes, there will always be a non-zero amount of electrons/positrons that escape and meet due to random processes. But the system will only run away exponentially if every single annihilation is guaranteed to cause at least one other annihilation some time later. I find this unlikely, given how easy it is for the resulting photon to just miss the plates entirely, knock electrons off in the wrong direction etc.

Let's say there are 1000 annihilations caused by temperature, cosmic radiation etc. every instant. If each annihilation has a 1/10 chance of causing another, at the next instant we'll have the base 1000 annihilations, plus another 100 caused by the ones at the previous instant, for a total of 1100. The next instant we'll have the base 1000, plus 110 caused by the ones at the previous instant, totalling 1110. The number converges towards 1111.1111... and thus we reach an equilibrium. The system will converge for any cascade probability less than 100%.

It really looks a lot like fission. There is always a non-zero amount of spontaneous fission. But it will only become self-sustaining under specific conditions.

[Domagoj T]

Unless you have just a tiny bit of ablation which knock a bit of material to the opposite side, causing much bigger event that quickly goes out of hand.

[calzap]

Let's not forget that electrons and positrons are attracted to each other unlike neutrons and nuclei in fission reactions.  So, any electron or positron that gets freed from its home plate has a  high probability of being annihilated.   Electron/positron annihilation produces two gamma rays of 512 KeV each traveling in opposite directions.  If the plates have lateral dimensions significantly larger than 1 micron, they are virtually certain to be struck by the gamma rays.  Whether the gamma rays interact depends on the elemental composition of the plates and their thickness.

Mike in California