Magnet Myths and Misconceptions

[TinselKoala]

TK:

A CRT is a regular circuit with a current loop.  The electrons leave the hot cathode (using FET lingo we can all that the source), and then are accelerated by the anode plates and then strike the phosphor.  Then there is a wire on the side of the CRT that acts as the drain for the electrons to complete the circuit.  I am assuming that there may be a voltage jump when the electrons flow from the drain wire back to the hot cathode to sustain the current loop also.  Sorry, I haven't looked at a CRT schematic in many years.

I don't see where you imply there is an issue. 

Here is what you said, that I was replying to:
"When you pass DC current through a conductor there is no "Newton balls" phenomenon taking place.  To me "Newton balls" implies electrons enter one end of a conductor and "push" on adjacent electrons to form a chain reaction where electrons at the opposite end of the conductor get "pushed out."  That is not happening."
But that is in fact _exactly_ what is happening. Where do the electrons come from in the cathode ray? THEY COME OUT OF THE WIRE that connects the cathode to the rest of the circuit. They are pushed through the wire by voltage... that is, the electric field, that comes from _individual unit charges_ pushing each other apart. That is what voltage IS !!!

There is an electric field making the electrons move through the current loop just like there is in a wire in a conventional circuit.  Note also that the beam of electrons can be induced to change direction by either an external electric field or by an external magnetic field.  Isn't it the yoke that produces the raster scan?  (i.e. "deflecting coils.) So the yoke is bending the electron beam because it's generating an external magnetic field where there are two "ramp" stimuli, one for the horizontal and one for the vertical.  I am assuming that there are CRTs that use horizontal and vertical ramp-function voltage potentials to do the same thing.  So instead of a yoke you have two sets of what look like big parallel plate capacitors, one for the horizontal and one for the vertical.

MileHigh

Do you think an electric field arises as if by magic? The gross electric field comes from having a bunch of tiny, like charges packed together. In situations where there is a varying electric field, like that surrounding a Tesla Coil, the field alternates in polarity at the frequency of _charges oscillating in the tank circuit_, bunching up first in the capacitor and then in the coil.
In a wire, electrons do move, they do come in at one end and go out the other end, as the cathode ray tube proves by allowing one to actually visualize the electrons flowing. They don't generally have to move at the speed of the signal in the wire, because of the Newton's Balls phenomenon where pressure is transferred without gross movements, but in situations like the CRT, it should be obvious that what comes out one end, has to go in the other end.
In a battery, the chemistry does indeed produce an excess of electrons at one pole and a deficit at the other pole. You are describing an electric field and I am telling you where the bulk field comes from in voltage sources: the charges of individual unit charges all added together. And it is the pressure resulting from these charges pushing each other away that IS voltage.
Experience with static machines, where huge charges are built up on surfaces by tiny currents over time, will teach one just what voltage is. In my Dirod, which is hand-cranked, you can actually _feel_ the additional work you do against the EF gradient to push more charge into the reservoirs. This is voltage! In generators you have charges being moved in conductors by moving magnetic fields. The mechanical force is transferred to moving charges and increasing charge pressure as the charges -- the electrons in the conduction band gas if you like-- are swept up and pushed together against their individual repulsions caused by their individual, tiny, fields from the unit charges they carry. If you like, you can just focus on the aggregate field and say that the field is pushing the charges along. But it is doing it as I illustrate, by the fields of individual charges pushing each other in the wire.  After all, the end of the wire connected to the cathode of the CRT can be very very long if I want it to be, far away from any fields that are providing the voltage in the wire in the first place. The wire "shorts" the field and brings its _effects_  (voltage, charge pressure) to the cathode ... and it does it by field pushing on field, little chunks travelling with each individual charge.

[TinselKoala]

MileHigh, I believe, your implication(s) on electrons behavior in DC (Direct Current) in solid conductor are scientifically supported. Can you show us a link or any reference on that matter?

Edit:

Oops! MH, you are supported: http://en.wikipedia.org/wiki/Charge_carrier

Then we have a dilemma.

There is nothing in that reference that contradicts what I have been saying and in fact it provides support for the conduction band electron gas, the charge pressure concept of voltage and etc.

[TinselKoala]

Continued...

So here is a thought experiment:   You have two batteries, one is 12 volts, the other one is one million volts.   There is no load on either battery.

When you look at the positive terminals of either battery, does the million-volt battery have more densely packed electrons on it?   (we will ignore the parasitic capacitance between the two terminals that will cause extra charge to appear on the terminals because we are not talking about that aspect.)

So, in my opinion, ignoring the parasitic capacitive effects, you will not observe any difference between the open-circuit positive terminals of each battery.  Both of the positive terminals, being made of metal, will be electrically neutral.   However, the potential of the electrons on the million-volt battery will be much higher that that of the 12-volt battery.

You are both right and wrong. "Potential" is a word that was used for voltage, for a good reason. In a battery, the potential is produced by chemical action and exists as Potential: the electrons haven't yet been released from their molecules in order to migrate across the circuit to neutralise the positive ions at the other terminal. But consider a capacitor instead of a battery. Here the charge is not "potential" it is really there and in the 1 million volt cap the whole thing is electrically neutral of course but there are certainly a lot more electrons on the negative side than on the positive side. And if you take the same _capacitance_ of capacitor and only charge it to one volt, there will be less charge _separation_ in the overall electrically neutral capacitor.

This is pretty "hard core" and I know my limits and all that stuff so I could be wrong in certain aspects.  By in general sense I am pretty confident that I am right.

Almost all circuits are driven by a voltage source.  That means the electric field is king.  The electric field snakes its way through all of the conductors in a circuit.   Some parts of the circuit, and some wires in the circuit may be at very high potential.  In cases like this you have a very very weak electric field inside the high-potential wires.  At the same time, the relative potential of the overall wire itself can be very high.   So you have a very weak electric field at a very high potential.  That may sound contradictory but in fact it's not.

Where you can get a very high electric field is in a resistor.  In wires the electric field strength is very very low, but in resistors the electric field strength can be very high (when you have a large voltage drop).  Sitting on top of all of this is the potential of any point in the circuit with respect to ground.

So you have two concepts of potential going on at the same time.  The first is the concept of relative potential to ground, and the second concept is the local differential potential.  In a wire the local differential potential is almost always very low.

And driving the whole thing is the electric field snaking its way through the wires.   The electrons are just along for the ride as all of this happens.  They don't get more closely bunched up at high voltage potentials.  If all of the electrons in a place in a circuit are at low potential, or if all of the electrons in a place in a circuit are at high potential, there is no difference in local electron density.

MileHigh

Wrong again. It's been a while since you've reviewed your vector calculus, I guess.
Where do you think "potential" comes from, if not from packing electrons (unit charges) closely together by doing work against the electric field they produce? What actually makes the voltage increase on the terminal of a VDG machine as the belt-drive motor works harder and harder as the voltage goes up?

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/diverg.html

[TinselKoala]

You may be right that there is a chemical coating on the cathode that facilitates the liberation of the electrons.  I honestly don't know.  When I read what you say I am wondering if a substance can act as a sort of catalyst for the liberation of the electrons.  But to be clear, "facilitating" is definitely not being a source of electrons.

For testing tubes, the filament can simply burn out like a light bulb.  I am guessing that that happens less frequently then the other failure mode.  That mode being when the tube loses its partial vacuum.  If the tube leaks and air enters, that will block the transmission of the electrons because they need a rarefied partial vacuum medium.

There are probably other failure modes.  I am old enough to remember tube testers being at the local pharmacy!  lol

It's scary to think that soon there will be adults that never saw CRT-based TVs for sale at Big Box stores, and adults that never walked into a video club to rent a movie!

MileHigh

Cathodes, and filament-cathodes, are coated with a material that facilitates the emission of electrons. You can have cold-field emission if the voltage is high enough, you can have emission from hot surfaces that is greater than the cold-field emission for the same voltage, and you can use materials from which it is easy to knock off electrons, and then you have the best of both worlds. You can get electron emission in greater quantity and at lower temperatures if you use a hot, thoriated cathode material. But the electrons still have to be replaced, they do not deplete in the cathode, they just flow through it. Residual gases or exceeding the tube's ratings can cause premature failure of cathodes but any old radio nut will tell you that you get the longest life from a thermionic tube by leaving it on, 24-7.

[TinselKoala]

There is no such thing as a "chemical with a rich supply of electrons available."   The cathode is effectively two things at the sane time.  It is the secondary load of a transformer, that's how it heats up.  This is completely isolated from the main circuit which is the second component.  The main circuit pumps electrons through the cathode such that they end up striking the phosphor screen.  The main circuit is the source of the electrons.  The main circuit is not even "aware" that the cathode is also a load resistor for the secondary of a transformer.

The heat facilitates the liberation of the electrons, somewhat akin to heating water facilitates the more rapid evaporation of the water.

And you forgot to mention that the Earth ground, in one form or another, replenishes the electrons that escape from the circuit by missing the anodes and striking the phosphor, so the circuit itself doesn't become depleted of electrons. The Earth is an essentially infinite sink and source of charge (electrons, holes). Which is which is determined by the local voltage level.