Electromagnetic field theory. Q and A

Actually, one Peter chapell(you may be knowing him from otherhealth BB for his AIDS PC1 remedy) has claimed somewhat that' taken some imprint & made some remedy from it).
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Whether or not his remedy works is one thing, but the guy clearly understands nothing about magnetism.

I wouldn't trust him to babysit my digital watch.

Onto more fruitful discussion material ...

An electric field is measured between two conductors with different charge, so no matter how far you put the wires apart you would have a 3V (Ithink it was 3V) between them, and the corresponding field. Whether it would be measurable is another story. Since the impedance is extremely high, it would certainly require very sophisticated equipment to detect it. The pole shift, when his relay trips, OTOH, should be detectable under laboratory conditions.
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Well yes, the device had some sort big plate as a cathode, so the other conductor was there ... I just assumed it would be possible to calculate the miniscully small field influence created theoretically. Just as, presumably one could calculate how far apart the two conductors would have to be before there was any flow of electrons or even spark. Is that possible at 3V? maybe in a vacuum?
 
Benguin:
Q: Well yes, the device had some sort big plate as a cathode, so the other conductor was there ... I just assumed it would be possible to calculate the miniscully small field influence created theoretically. Just as, presumably one could calculate how far apart the two conductors would have to be before there was any flow of electrons or even spark. Is that possible at 3V? maybe in a vacuum?

A: Well, if the plates were 1m apart, the field would be 3 V/m, and I'm sure the attraction betwee nthe plates can be calculated, although I'd have to do some Googling to find the formula.

In a vaccum, the field could create a flow of electrons, provided free electrons were available.

We cannot just change the distance, because then the charge will change. That is immaterial if the plates are connected to a power source, but suppose we just had the two plates floating in space. They are one m apart, and the field is 3 V/m. Now we move them closer, to 1/5m, will the field now be 6 V/m? No, because with the shorter distance, the capacitance will increase, and since the charge is the same, the voltage will now be lower. Likewise, if we move the plates out to two m (or to opposite sides of the galaxy), the capacitance will fall, but since it must hold the same charge, the voltage will rise accordingly.

Oh, and essentially, sparks do not occur in a vacuum, because sparks are ionized paths in air.

Hans
 
69dodge said:
Static electric and magnetic fields can be described in terms of virtual photons, which are not quite the same thing as regular photons.
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Right, because a regular photon carries energy, which as mentioned, the field does not. But like anything else, it has a quantum particle.

Hans
 
Why do those rubber refrigerator magnets seem to have parallel linear ridges in their fields? Why does putting them in a strong magnetic field make them not stick to the fridge anymore? How can I reactivate all the nice ones I've ruined?

What's the deal with the points on lightning rods; are they supposed to be sharp, rounded, or what?
 
I saw an idea several years ago about shooting powerful lasers at thunderstorms to effect the lightning. I forget what it was supposed to do. Could you fill me in on it? Is it a credible idea?
 
MRC_Hans said:
A: Well, if the plates were 1m apart, the field would be 3 V/m, and I'm sure the attraction betwee nthe plates can be calculated, although I'd have to do some Googling to find the formula.

In a vaccum, the field could create a flow of electrons, provided free electrons were available.

We cannot just change the distance, because then the charge will change. That is immaterial if the plates are connected to a power source, but suppose we just had the two plates floating in space. They are one m apart, and the field is 3 V/m. Now we move them closer, to 1/5m, will the field now be 6 V/m? No, because with the shorter distance, the capacitance will increase, and since the charge is the same, the voltage will now be lower. Likewise, if we move the plates out to two m (or to opposite sides of the galaxy), the capacitance will fall, but since it must hold the same charge, the voltage will rise accordingly.
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OK, thanks. I was trying to come up with a genuine theoretical picture of what was happening and the miniscule forces and field effects involved.



Oh, and essentially, sparks do not occur in a vacuum, because sparks are ionized paths in air.
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Hans
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Doh! Yes of course.
 
MRC_Hans said:
Oh, and essentially, sparks do not occur in a vacuum, because sparks are ionized paths in air. [/color]

Hans
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Hmm...

So, Hans, what is the breakdown field strength of dry air, and what is the breakdown strength of a vacuum?

What happens when one exceeds the breakdown strength in the vacuum?
 
Isn't an issue of the visual element of the spark being caused by atmospheric molecules glowing with excitement?
 
jj said:
Hmm...

So, Hans, what is the breakdown field strength of dry air, and what is the breakdown strength of a vacuum?

What happens when one exceeds the breakdown strength in the vacuum?
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Air: 3x10<sup>6</sup> V/m

Vaccuum is going to be rather close to that since air's dielectric coefficient is close to 1 (dielectric coefficient = permittivity of substance / permittivity of vacuum).

To give Hans some help (if he wants it, please feel free to ask me not to answer until you have had a chance, Hans, I am sure my credentials are nowhere near yours in this field):

Sparks are not electrons. They are the byproduct of electrons traveling via holes in the electron shells in the intervening atoms in the air. Their "jumping" from atom to atom and shell to shell releases energy.

When one exceeds breakdown strength in a vaccuum, electrons flow, you just don't *see*anything. You can detect it by the magnetic field it would produce, though. In reality, I would think the electron flow would heat up and ionize any conductors (how else do you get electrons into a vaccuum), resulting in some sort of visual glow from the ionized atoms that are ejected from the leads... though probably very faint.
 
Gestahl said:
When one exceeds breakdown strength in a vaccuum, electrons flow, you just don't *see*anything. You can detect it by the magnetic field it would produce, though. In reality, I would think the electron flow would heat up and ionize any conductors (how else do you get electrons into a vaccuum), resulting in some sort of visual glow from the ionized atoms that are ejected from the leads... though probably very faint.
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If an electron moves because of an electric field, it is losing energy. So if two plates across a vacuum are charged until the vacuum breaks down, presumably the electrons are going to lose a heck of a lot of energy. Since the movement of said electrons changes the electric field, I assume that lose will result in the emission of a photon.

So if the the plates were far enough apart that the energy loss of a single electron was significant enough some of those photons may be in the visible spectrum. So presumably with enough charge creating photons one may see a flash.

Walt
 
Gestahl said:

Sparks are not electrons. They are the byproduct of electrons traveling via holes in the electron shells in the intervening atoms in the air. Their "jumping" from atom to atom and shell to shell releases energy.

When one exceeds breakdown strength in a vaccuum, electrons flow, you just don't *see*anything. You can detect it by the magnetic field it would produce, though. In reality, I would think the electron flow would heat up and ionize any conductors (how else do you get electrons into a vaccuum), resulting in some sort of visual glow from the ionized atoms that are ejected from the leads... though probably very faint.
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Mr.Hans,

It is interesting.;)
 
phildonnia said:
What's the deal with the points on lightning rods; are they supposed to be sharp, rounded, or what?
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There was an exhibit at the science museum in Flushing, New York about 35 years ago about this. You could manually bring several different shaped toward a charged Van de Graff sphere. The pointed one sparked at a further distance. At the time, when I was a kid, I thought that this was because there were more electrons that had to make a sharper turn at the point not to fly off. I also thought this was why when you were charged by a Tesla coil, sparks tended to come off the fingertips before elsewhere. This is probably wrong, but I haven't thought about it since then.
 
They have an incredibly good gallery (with demonstrations) in the Museum of Science and Technology in Munich.

I'm surprised the Science Museum in London hasn't emulated it.
 
phildonnia:

Q: Why do those rubber refrigerator magnets seem to have parallel linear ridges in their fields?

A: They are magnetized in stripes of north and south poles, to get the best attraction from the relatively weak magnets.

Q: Why does putting them in a strong magnetic field make them not stick to the fridge anymore?

A: The material is not a good magnetism retainer, so a strong magnet will reorient it, probably with a single set of north and south poles, which is not nearly as effective as the striped arrangement.

Q: How can I reactivate all the nice ones I've ruined?

A: All?? A slow learner, huh? Well, I suppose you could buy some cheap ones and swap the magentic rubber. You can probably stick it to the nice tops with contact glue.

Q: What's the deal with the points on lightning rods; are they supposed to be sharp, rounded, or what?


Ideally, a sharp point will start ionization a little better, and thus be more effective, but once lightning is headed your way, I doubt if it makes much difference.

Hans
 
Gestahl said:
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To give Hans some help (if he wants it, please feel free to ask me not to answer until you have had a chance, Hans, I am sure my credentials are nowhere near yours in this field):
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You are very welcome! I'm glad this thread has turned out so popular, but I might lack hopelessly behind without help. As for credentials, I'm just an electronic engineer, but anyway, it's not credentials this is about, it is about answers.

Hans :)
 
About electrons moving in a vacuum, this is what ye olde vacuum tubes are all about. Here, the cathode is heated to make it emit electrons, which are then made to flow in the vacuum of the tube. In vacuum tubes, you will sometimes see a faint blue glow around the anode, but I'm not sure exactly what causes it.

On my homepage, here are several articles, including one about vacuum tubes, which saves me the trouble of describing it here ;).

Hans
 
Walter Wayne said:
If an electron moves because of an electric field, it is losing energy. So if two plates across a vacuum are charged until the vacuum breaks down, presumably the electrons are going to lose a heck of a lot of energy. Since the movement of said electrons changes the electric field, I assume that lose will result in the emission of a photon.

So if the the plates were far enough apart that the energy loss of a single electron was significant enough some of those photons may be in the visible spectrum. So presumably with enough charge creating photons one may see a flash.

Walt
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Mmm, I have to disagree here. An electron moving in a vacuum will, once accelerated, simply keep moving till something intercepts it. If it is inside an electic field, it will keep accelerating till it impacts with the positive elctrode.

Hans
 
I would like to understand the process by which a photon is emitted a little better.

I understand that when an electron moves from a higher energy state to a lower energy state within an atom a photon is emitted and the frequency of that photon is proportional to the energy difference between the energy states that the electron transitioned between when the photon was generated.

OK, atoms jiggling back and forth from thermal energy also cause photons to be generated as with infrared radiation. I assume a somewhat similar mechanism is going on here as the one that generates the photons from electron state transitions within an atom. Could somebody provide a little bit more detail about this. Apparently the electrons are being accelerated by the atoms kinetic motion and this acceleration is resulting in the generation of a photon. OK, at what point in the acceleration of the electron is the photon being generated? Ah, a thought: Maybe the thermal motion is causing the electons to transition to higher energy levels within the atom and the transition of the electron to ground state is what actually generates the infrared photon?

All right, how does the generation of these higher frequency photons relate to the generation of photons in an antenna? Somehow moving the free electrons back and forth in the antenna causes the antenna to emit a series of photons. What is necessary to cause the antenna to emit just one photon? How many cycles are present in a single photon? Can a single photon at say a 100MHz be detected? What kinds of single photons be detected?
 
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