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Author Topic: Magnet Myths and Misconceptions  (Read 605779 times)

TinselKoala

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Re: Magnet Myths and Misconceptions
« Reply #150 on: October 10, 2014, 07:36:46 AM »
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 !!!

Quote

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

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Re: Magnet Myths and Misconceptions
« Reply #151 on: October 10, 2014, 07:38:23 AM »
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

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Re: Magnet Myths and Misconceptions
« Reply #152 on: October 10, 2014, 07:46:58 AM »
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.
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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

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Re: Magnet Myths and Misconceptions
« Reply #153 on: October 10, 2014, 07:54:09 AM »
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

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Re: Magnet Myths and Misconceptions
« Reply #154 on: October 10, 2014, 07:57:52 AM »
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.

Newton II

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Re: Magnet Myths and Misconceptions
« Reply #155 on: October 10, 2014, 08:03:13 AM »

@milehigh,


I meant a charged isolated conductor only.  So, your answer is 'YES'.

'A moving, charged isolated conductor produces  magnetic field'

1) In any purely mechanical system, work is 'force X distance'.  So, energy, which is total capacity you have, to do   work (either in faster
    rate or slowly) is conserved and total input energy equals the total output energy.

2) So, when you move a charged conductor applying mechanical force, its input and output energy is conserved as or used up as purely
     mechanical energy.    Then from where the charged conductor gets energy to produce magnetic  field which represents electrical energy?

3) Does it mean that magnetic field is created out of nothing? (I mean without input energy?)   
   
4) Does it also mean that moving charged conductor digs out energy from the vaccuum to create magnetic field?

5) Why should a moving charge produce magnetic field at any cost?   Either moving under the influence of electric potential or under
     mechanical force?

6) Does it mean that a magnetic field is absolutely necessary for a moving charge?

7) Does it also  mean that nature prefers creation of magnetic field more than conservation of energy?



TinselKoala

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Re: Magnet Myths and Misconceptions
« Reply #156 on: October 10, 2014, 08:16:33 AM »
Mostly it means that your assumptions are still screwed up.

There is only ONE field, the electromagnetic field. Which aspect of it you experience depends on relative motion. If you move along with a moving charge you cannot detect any magnetic field from it, only electric field. But if you are stationary and that same charge moves past you at the same velocity, you see a magnetic field around the path of motion.


Look,  no magnets and no perceptible magnetic field (except in the belt drive motor):
http://www.youtube.com/watch?v=cj5T0zRALKc

Yet the capacitor is charging up with the same kind of voltage that is produced by a generator using magnetic fields. There is only one kind of voltage, and that is charge pressure caused by increasing charge density... and since the electron, a point particle, is the carrier of the unit negative charge, the only way to increase charge density in conductors is to do work against all those little electric fields, forcing more electrons to occupy the same space.

TinselKoala

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Re: Magnet Myths and Misconceptions
« Reply #157 on: October 10, 2014, 08:45:20 AM »
@MH: Where does the voltage in a battery come from? Yes, it comes from an excess of electrons at one terminal and a deficit of them at the other terminal, and this is produced by the action of the imposed electric field from an external voltage source, on ions during charging.

http://en.wikipedia.org/wiki/Battery_%28electricity%29

http://en.wikipedia.org/wiki/Electrochemical_potential

Newton II

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Re: Magnet Myths and Misconceptions
« Reply #158 on: October 10, 2014, 09:50:01 AM »

Mostly it means that your assumptions are still screwed up.


Agreed.  I am tightly screwed to ground by a screw jack on my ass.  A charged conductor passes infront of me with terrific speed and I would see a magnetic field around it.  After moving through some distance the conductor stops due to some reason.  So, I will see an electric field around the conductor.

But when magnetic field becomes electric field, I would also see some energy  released by 'self induction' or mutual induction.  What happens to that energy?  Will it come to me and further tighten the screw jack on my ass?
 
If I am blind I would neither see a magnetic field nor electric field but would only feel screw jack getting tightened on my ass.

Input energy = 100% mechanical energy

Output energy = 100% mechanical energy  + Energy released by collapsing magnetic field (energy received from where?)



Look,  no magnets and no perceptible magnetic field (except in the belt drive motor):
http://www.youtube.com/watch?v=cj5T0zRALKc

Yet the capacitor is charging up with the same kind of voltage that is produced by a generator using magnetic fields. There is only one kind of voltage, and that is charge pressure caused by increasing charge density... and since the electron, a point particle, is the carrier of the unit negative charge, the only way to increase charge density in conductors is to do work against all those little electric fields, forcing more electrons to occupy the same space.

I agree with all that.   But as you can see my question is different.   It is about a moving charged conductor producing a magnetic field (even
if it is an illusion) and releasing energy when field collapses.  This energy comes from where?   We are not doing any work on charges because the charges are also moving with the conductor as its integral part.



Magluvin

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Re: Magnet Myths and Misconceptions
« Reply #159 on: October 11, 2014, 12:12:52 AM »

off that topic, I had an idea to wind a copper wire around a plastic toroid, 4in dia, 1/2in thick, 1/2in deep.  1 layer. Then make a rotor with all magnets N pointing out. just used 2 mags in the test.  It was a slap together thing, a bit off balance in every way, but just tried.  When I applied current to the coil, sometimes the rotor turned CW, sometimes CCW.  The idea was to have the mags close to the inside part of the coil and have the N poles of the mags ride the field spin around those inner windings.  As in a DC motor without pole switching. I chose to use a non magnetic core so as not to have it absorb the field away from the mags.  But a core may help, havnt gotten there yet. Busy with life. Try to get to some experiments here n there. ;) Just throwing it out there. ;) ;D


Mags


Had an idea to build this a 'lil bit' differently.  Will draw it up later in 3D to show what im thinking before I build it.

Mags

allcanadian

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Re: Magnet Myths and Misconceptions
« Reply #160 on: October 11, 2014, 02:31:55 AM »
@TinselKoala
Quote
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!
Dirod you say?, you know it's funny how one simple word can explain so many things about a person and I built my first Dirod, a Van de Graaff and a Bennett doubler a decade or so ago. I still have A.D.Moores book on electrostatics in the nightstand next to my bed and I am pretty sure I learned more from that book and my simple experiments than most people learn in a lifetime concerning electricity. I'm glad you chimed in as the voice of reason because what I was reading prior was ridiculous in my opinion.
AC
 

Pirate88179

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Re: Magnet Myths and Misconceptions
« Reply #161 on: October 11, 2014, 04:07:36 AM »
TK:

So, in view of your postings and MH's postings, as well as others, am I to conclude that my circa 1980's electronics text books might have it wrong when they say that, in a circuit, the energy (electrons) flows from positive to the negative.  (Like flowing to ground, which I have always been told)  I have since read (In newer books) that even though the schematic symbol for a diode shows an arrow, the energy flows the opposite way in any circuit.  (From - to +) So, if I am designing a small circuit, or looking at a schematic, would it be better for me to trace the flow from the minus, through the circuit to the positive input?  This seems counter intuitive from what I (thought) I learned all these years playing around.

If I am building a JT type circuit,  I look at the positive end of the battery and trace the flow of "energy" to the resistor, to the base of the transistor...etc.  Does it really matter which way the energy flows?  (although I would really like to know for myself)  I mean, my circuits (most of them) work but, if those older books are indeed outdated, it would be good for me to know.  Is it possible that no one "really" knows?  Or, has something in research since the 80's changed this way of looking at a circuit?

I really do not mean to sound like an idiot here.  You know me and my skill level.  I build some cool things and can do some cool stuff, but other stuff is waaay over my head.  I am trying to fix this.

Thank you,

Bill

TinselKoala

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Re: Magnet Myths and Misconceptions
« Reply #162 on: October 11, 2014, 07:24:39 AM »
@TinselKoalaDirod you say?, you know it's funny how one simple word can explain so many things about a person and I built my first Dirod, a Van de Graaff and a Bennett doubler a decade or so ago. I still have A.D.Moores book on electrostatics in the nightstand next to my bed and I am pretty sure I learned more from that book and my simple experiments than most people learn in a lifetime concerning electricity. I'm glad you chimed in as the voice of reason because what I was reading prior was ridiculous in my opinion.
AC

Well, thanks.  I'd love to see your Dirod, they are rare as hen's teeth. I think I've only seen videos of two or three others on YT.  Yes, AD Moore's book inspired my electrostatic explorations and I also got a lot from Richard Ford's "Homemade Lightning" book. I built my Dirod in 1999. Later on I got a lot of inspiration from the work of Oleg Jefimenko.

Here's my Dirod in action:

http://www.youtube.com/watch?v=OxEpSX2Hd54
http://www.youtube.com/watch?v=vqf3bUL4YqE
http://www.youtube.com/watch?v=YpemKuf6X_c
And a little VDG machine and a calibrated ES voltmeter:
http://www.youtube.com/watch?v=eogpGHFgV6E

So, some discussion questions for the audience: Is there current flowing in the above demonstration? If so, in which direction?
There are no magnets anywhere in the Dirod or the ppb oscillator or other demo devices shown. How does the system work? Is there a difference between the electricity in the spark at the end of the demos, and the electricity I might have gotten from a power supply or battery to charge up the capacitor bank? Where did the _voltage_ come from? Are the bead chain links charged, or not?

TinselKoala

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Re: Magnet Myths and Misconceptions
« Reply #163 on: October 11, 2014, 07:37:27 AM »
TK:

So, in view of your postings and MH's postings, as well as others, am I to conclude that my circa 1980's electronics text books might have it wrong when they say that, in a circuit, the energy (electrons) flows from positive to the negative.  (Like flowing to ground, which I have always been told)  I have since read (In newer books) that even though the schematic symbol for a diode shows an arrow, the energy flows the opposite way in any circuit.  (From - to +) So, if I am designing a small circuit, or looking at a schematic, would it be better for me to trace the flow from the minus, through the circuit to the positive input?  This seems counter intuitive from what I (thought) I learned all these years playing around.

If I am building a JT type circuit,  I look at the positive end of the battery and trace the flow of "energy" to the resistor, to the base of the transistor...etc.  Does it really matter which way the energy flows?  (although I would really like to know for myself)  I mean, my circuits (most of them) work but, if those older books are indeed outdated, it would be good for me to know.  Is it possible that no one "really" knows?  Or, has something in research since the 80's changed this way of looking at a circuit?

I really do not mean to sound like an idiot here.  You know me and my skill level.  I build some cool things and can do some cool stuff, but other stuff is waaay over my head.  I am trying to fix this.

Thank you,

Bill
Long before anyone actually discovered the electron and understood that it carried a unit charge and so forth, Benjamin Franklin, who was a great scientist and experimenter, decided that electricity was a kind of fluid that had two characters that he called "negative" and "positive". He made a W.A.G. and assigned the label "negative" to the polarity (of chemical batteries and electrostatic charges) that we now know is actually the source of electrons. And we know that the "flowing" electrons move in the direction from Franklin's "negative" polarity towards the "positive" polarity in actuality and it is this motion of charge that transfers the energy, that is does the work, in an electrical circuit.

But most of the math was worked out before the actual discovery of the electron itself and the realization that it was the fundamental charge carrier in circuits! And the electron is stuck with the label "negative" because of Franklin's wild-ass guess.

So your textbooks are right: the formulae and all the rest of electrical engineering math is stuck with Franklin's conventional flow of "electricity" fluid from Positive to Negative. The Anode is the arrow -> pointing from the more positive polarity to the more negative (or less positive, same thing). It's a convention, that's all, like driving on the left side of the road in the UK.

And the present understanding is also right: the actual flow of charge goes from Negative to Positive. But so what? The math is based on the other side of the convention, they are just words. There is nothing inherently "negative" or "positive" about electrons, protons and charge! Franklin could just as well have called them Male and Female, as he felt that there were indeed two fluids involved in his concept of electricity.

So when you do your circuit analysis, choose components, calculate power, etc etc, you use the convention of electricity flowing from positive to negative polarity. But if you want to understand what is happening on a deeper level, a quantum level if you will, then you must leave convention where it belongs and start looking at the underlying phenomena, including electrons as charge carriers travelling in the opposite direction to the conventional Anode arrows, etc.

Pirate88179

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Re: Magnet Myths and Misconceptions
« Reply #164 on: October 11, 2014, 07:54:45 AM »
TK:

Thank you for that great answer.  I really do appreciate that more than you know.  I am attempting to fill in the gaps in my knowledge and, the more I learn, the more gaps I find that I have.

Thanks again,

Bill