A resistor that never gets hot?

[John Heath]

This being the case Tina could screw it up for real life simulation.

It is a poor craftsman who blames his tools.

The model is only as good as the squishy meat-computer commanding it. If you told it to model an all-pole system, you should expect it to tell you nothing other than the properties of that system; you certainly should not expect an ideal transmission line, as that would be expecting the computer to do something completely different from what it was told!

"Pray tell, Mr. Babbage; if one should enter incorrect numbers in the Engine, can it still produce the correct result?"

Tim

Yes and no. I will tell Tina to drive a given transistor with a 10K resistor thinking the output on the collector output will be bigger but the same. Tina says no no no it will not be the same b/c , b/e capacitance , gain. Tina says you can not have the high frequencies therefore your output will look like this. Tina has taken on the responsibilities of thinking on her own using her data base of the specified transistor being used. The way I see it is in for a penny in for a pound. At high enough frequencies not only inductance of the circuit but the mass of the electron itself has to be added for total inductance. Will Tina compensate for this? In for a penny in for a pound so why not?   

[T3sl4co1l]

I think I have a handle on domain hysteresis and eddy currents but skin effect I do not understand. Why do electrons prefer scooting alone the skin of copper? If I hammer a copper round wire flat does it have less resistance as there is now more surface skin that the electrons like? If you can shed some light on this I would not mind hearing it.

As you go up in frequency, the changing magnetic field around the wire affects the wire itself.

Imagine a round wire (isolated in space, nothing near it) divided into concentric shells.  The outermost shell encloses all the current carried by the interior, which therefore produces a magnetic field in the outermost shell (which is nearly the magnetic field at the surface of the wire -- just add the current of the outermost shell).  This field is changing, so it induces a current in the conductor, which opposes the current flow.  How much does it oppose?  Depends on the resistance of the shell: circumference times resistivity of the material.  As you go from inside to outside, the enclosed current increases, but so does the circumference; but area increases faster, so the current would actually be flipped, becoming negative on the outside -- as a result of assuming a constant (evenly distributed) current on the inside.  This is a contradiction, so we know the current cannot be even!

In fact, it's a feedback mechanism, where most of the current flows on the outside, and the current inside is determined by what current (and magnetic field) is left after passing through the outer shell, and so on.

At very high frequencies, hardly any energy flows in the conductor itself, rather it's contained entirely within the space around the conductor.  The conductor is a boundary condition, shaping the EM field, but not directly participating.  This is true of ordinary TEM (stripline, coax, etc.) sorts of transmission lines, and even more explicit in waveguides (including the all-dielectric kind, and fiber optics), Goubau lines, and free waves.

It's maybe more convenient to assume the energy is contained in the space around the conductor, and 'seeps' into the conductor.  If instead of AC steady state, we think in terms of transient time, then: when a step change occurs, first the change propagates at the speed of light, in the space around the conductor.  This imposes a current on the surface of the conductor, and an opposing magnetic field.
 Because the change is very rapid, the surface depth is very shallow (less than a micron, say).  As time goes on, the rate of change outside the conductor remains zero (it's a step), but the rate of change within the conductor is nonzero: the magnetic field, and current flow, diffuse into the conductor.

Still another way to think of it: the conductor has a very high index of refraction.  This is nonsense, right?  I mean it's a conductor...  Well, refractive index is determined by permeability and permittivity; and permittivity is how 'conductive' a substance is to electric fields.  Normally it gives capacitance, but if we merely expand this to the complex plane -- as is normal for AC steady state problems, anyway -- we can consider a complex capacitor, which gives real resistance.  Thus, bulk resistivity is identical to complex permittivity.  The magnitude of the index is large, but it's very lossy as well.  Indeed, this tells us metals are good shields -- incident radiation is primarily reflected (because of the huge index mismatch), and what's left is quickly absorbed.  If we think about how a wave propagates through such a material, its amplitude decays as it goes (because of the loss), while being phase shifted.  If we look at the average effect, we see diffusion.

Indeed, wave mechanics don't go away just because you've put down a conductor -- can you do standing waves in a conductor?  Absolutely.  For a moderately sized round wire (i.e., radius about 1-3 skin depths), the wave doesn't fully attenuate by the time it reaches the center; waves coming in from all sides means the center is a null.  At certain frequencies, there are also zeroes away from center, so that current density is large at the surface, dropping to zero at some inner shell, then actually going backwards in the core (before again going to zero at the center).

Or for a sheet, a particular thickness of foil/film can have a color.  Hold a CD-ROM up to the light, and see that it looks not completely opaque, but slightly bluish.  That's a thin (100nm??) film of aluminum metal you're seeing through.

What does this mean for oddly shaped conductors?  Transformers?  Other structures?  What if we want more current, or less (for that matter)?

A ribbon shaped conductor, in isolation, is worse than a round wire.  Consider where the magnetic field must go: for the round case, it is evenly distributed around the wire, and current density can't be any lower.  For an oblong shape, the magnetic field will clip into the peaks, increasing current density there, and reducing efficiency.

What if the conductor is not in isolation, but near other wires carrying currents?  Well, all those currents act together, shaping the current distribution in each wire.  A pair of wires carrying opposite currents (twin lead) has the magnetic field canceling out at far distances -- which means the back sides of the wires carry little current.  The magnetic field is concentrated in the space between wires, and so the currents are concentrated on the facing sides of the wires.

Likewise, two wires carrying equal currents (same direction) repel.  (Kind of like skin effect all over again, just with the conductor broken up into pieces.)

In a transformer, say you have a windup like this: 2 layers secondary, tape, 2 layers primary.  Take a cross section, and you will see pairs of wires in the same direction (the two layers), and pairs opposing (the two layers separated by tape).  The layers in the middle there have double trouble: they're being pinched by the currents outside of them, while also facing opposite currents.  This double-pinches the current, so the inner layers have even worse distribution.  This is proximity effect.

You avoid proximity effect by interleaving opposing currents.  Suppose the transformer were wound: (1 layer each) P, S, P, S.  The middle layers are pinched the same way in two directions at once, resulting in more even current distribution.

What else can we do?  If we go back to the flat conductors, but use two carrying opposing currents, we can spread out the current by placing them broadside-facing.  This works for transformers with single turn foil windings, PCB traces (particularly in multilayer boards when you need to move a lot of AC current around) and so on.

So, is flat conductor better?  Not alone, but when used correctly -- near opposing currents, flat to flat, it's much better.

By the way, the space between wires -- that's carrying all that close-up magnetic field -- is the leakage inductance in a transformer.  The interleaved case has less leakage, which is a big help for most switching converters.

Tim

[John Heath]

I think I have a handle on domain hysteresis and eddy currents but skin effect I do not understand. Why do electrons prefer scooting alone the skin of copper? If I hammer a copper round wire flat does it have less resistance as there is now more surface skin that the electrons like? If you can shed some light on this I would not mind hearing it.

As you go up in frequency, the changing magnetic field around the wire affects the wire itself.

Imagine a round wire (isolated in space, nothing near it) divided into concentric shells.  The outermost shell encloses all the current carried by the interior, which therefore produces a magnetic field in the outermost shell (which is nearly the magnetic field at the surface of the wire -- just add the current of the outermost shell).  This field is changing, so it induces a current in the conductor, which opposes the current flow.  How much does it oppose?  Depends on the resistance of the shell: circumference times resistivity of the material.  As you go from inside to outside, the enclosed current increases, but so does the circumference; but area increases faster, so the current would actually be flipped, becoming negative on the outside -- as a result of assuming a constant (evenly distributed) current on the inside.  This is a contradiction, so we know the current cannot be even!

In fact, it's a feedback mechanism, where most of the current flows on the outside, and the current inside is determined by what current (and magnetic field) is left after passing through the outer shell, and so on.

At very high frequencies, hardly any energy flows in the conductor itself, rather it's contained entirely within the space around the conductor.  The conductor is a boundary condition, shaping the EM field, but not directly participating.  This is true of ordinary TEM (stripline, coax, etc.) sorts of transmission lines, and even more explicit in waveguides (including the all-dielectric kind, and fiber optics), Goubau lines, and free waves.

It's maybe more convenient to assume the energy is contained in the space around the conductor, and 'seeps' into the conductor.  If instead of AC steady state, we think in terms of transient time, then: when a step change occurs, first the change propagates at the speed of light, in the space around the conductor.  This imposes a current on the surface of the conductor, and an opposing magnetic field.
 Because the change is very rapid, the surface depth is very shallow (less than a micron, say).  As time goes on, the rate of change outside the conductor remains zero (it's a step), but the rate of change within the conductor is nonzero: the magnetic field, and current flow, diffuse into the conductor.

Still another way to think of it: the conductor has a very high index of refraction.  This is nonsense, right?  I mean it's a conductor...  Well, refractive index is determined by permeability and permittivity; and permittivity is how 'conductive' a substance is to electric fields.  Normally it gives capacitance, but if we merely expand this to the complex plane -- as is normal for AC steady state problems, anyway -- we can consider a complex capacitor, which gives real resistance.  Thus, bulk resistivity is identical to complex permittivity.  The magnitude of the index is large, but it's very lossy as well.  Indeed, this tells us metals are good shields -- incident radiation is primarily reflected (because of the huge index mismatch), and what's left is quickly absorbed.  If we think about how a wave propagates through such a material, its amplitude decays as it goes (because of the loss), while being phase shifted.  If we look at the average effect, we see diffusion.

Indeed, wave mechanics don't go away just because you've put down a conductor -- can you do standing waves in a conductor?  Absolutely.  For a moderately sized round wire (i.e., radius about 1-3 skin depths), the wave doesn't fully attenuate by the time it reaches the center; waves coming in from all sides means the center is a null.  At certain frequencies, there are also zeroes away from center, so that current density is large at the surface, dropping to zero at some inner shell, then actually going backwards in the core (before again going to zero at the center).

Or for a sheet, a particular thickness of foil/film can have a color.  Hold a CD-ROM up to the light, and see that it looks not completely opaque, but slightly bluish.  That's a thin (100nm??) film of aluminum metal you're seeing through.

What does this mean for oddly shaped conductors?  Transformers?  Other structures?  What if we want more current, or less (for that matter)?

A ribbon shaped conductor, in isolation, is worse than a round wire.  Consider where the magnetic field must go: for the round case, it is evenly distributed around the wire, and current density can't be any lower.  For an oblong shape, the magnetic field will clip into the peaks, increasing current density there, and reducing efficiency.

What if the conductor is not in isolation, but near other wires carrying currents?  Well, all those currents act together, shaping the current distribution in each wire.  A pair of wires carrying opposite currents (twin lead) has the magnetic field canceling out at far distances -- which means the back sides of the wires carry little current.  The magnetic field is concentrated in the space between wires, and so the currents are concentrated on the facing sides of the wires.

Likewise, two wires carrying equal currents (same direction) repel.  (Kind of like skin effect all over again, just with the conductor broken up into pieces.)

In a transformer, say you have a windup like this: 2 layers secondary, tape, 2 layers primary.  Take a cross section, and you will see pairs of wires in the same direction (the two layers), and pairs opposing (the two layers separated by tape).  The layers in the middle there have double trouble: they're being pinched by the currents outside of them, while also facing opposite currents.  This double-pinches the current, so the inner layers have even worse distribution.  This is proximity effect.

You avoid proximity effect by interleaving opposing currents.  Suppose the transformer were wound: (1 layer each) P, S, P, S.  The middle layers are pinched the same way in two directions at once, resulting in more even current distribution.

What else can we do?  If we go back to the flat conductors, but use two carrying opposing currents, we can spread out the current by placing them broadside-facing.  This works for transformers with single turn foil windings, PCB traces (particularly in multilayer boards when you need to move a lot of AC current around) and so on.

So, is flat conductor better?  Not alone, but when used correctly -- near opposing currents, flat to flat, it's much better.

By the way, the space between wires -- that's carrying all that close-up magnetic field -- is the leakage inductance in a transformer.  The interleaved case has less leakage, which is a big help for most switching converters.

Tim

Thank you for a quality post. I can see you are using different analogies hoping one of them will get the point across. I got some of it but not all.
A few questions.

A] 100 amps filtered DC going through a wire. No skin effect zip nada zero. Yes / no ?
B] For AC current. Less inductance on the outside , skin , of the wire so more current on the skin . Yes / no?
C] A and B are correct but it is not that simple. Yes / no ?

If I have A and B right then it only leaves C "not that simple"


If your answer to A is yes and B is yes is It is mcounter EMF 

[T3sl4co1l]

Thank you for a quality post. I can see you are using different analogies hoping one of them will get the point across. I got some of it but not all.
A few questions.

A] 100 amps filtered DC going through a wire. No skin effect zip nada zero. Yes / no ?

None, current density is evenly distributed (according to resistivity and Ohm's law in bulk material).

B] For AC current. Less inductance on the outside , skin , of the wire so more current on the skin . Yes / no?
...
If your answer to A is yes and B is yes is It is mcounter EMF

Is is?

There's always EMF, but tracking the EMF around and within a wire doesn't seem as useful to me.

Inductance isn't the motivating factor here -- it's not like, say, an equivalent circuit where there's a bunch of independent current paths wired in parallel, and current distributes according to their impedances.  It's more like a ladder diagram, where there's two terminals (the external fields at the surface, where you can probe / connect to it), then a chain of alternating series and parallel components (namely, L and R), where the further down the chain you go, corresponds to depth beneath the surface.  Only at DC do the resistors all connect in parallel (X_L = 0), while at higher frequencies, the L's cut off some of the resistance, causing R_AC to rise and concentrating current flow towards the surface.

Tim

[John Heath]

Where are my ICs in the Tina9 software? I see a 555 timer and an op-amp. Where is the 4000 series and 74hc series of ICs. Do I have to down load these separately?

These type of SPICE simulators are primarily for doing analog simulation, not digital. (Not to say you can’t; I know there are limited sets of 4000 and 74 series models for LTspice, for example, but these type of packages don’t excel pure at digital simulation, since they will be simulating the analog characteristics of each transistor and FET of the part.)

You should also know that SPICE simulators like this aren’t intended to simulate an entire large circuit in a single go. You’re meant to break it up into smaller chunks. (If you need to use the output of one chunk as the input of another, you can save the output as a waveform (PWL file) and then use it as an input later.)

Anyway, based on your OP we thought you needed a good analog simulator. If you want to do fast digital simulation we can recommend some software for that.o

I was looking at some more videos on Tina. Apparently there are Tinas and there are TINAS . I took a picture off the videos so you can see the difference between Tina and TINA TINA gets optoelectronics , your choice of logic ICs , a bunch of MCUs , A/D D/A converters , the list go on and on. What did I get in the "Tina package" one stinking 555 timer ?  What am I supposed to do with that blink a  LED on and off? What am I chicken liver here? Why does TINA get all the good stuff while I am stuck with one stinking 555 timer? Pardon the humor as I need the practice. I am sure it is a Tina library add on. Just wondering where to find this Tina library add on for those MPUs and such?

The full version of TINA is a commercial package and costs several hundred dollars to start. However, TI offers models that will work in their cut down version of TINA. Also, most other standard Berkeley SPICE models will work, but these are full analog simulations of the digital parts, so it will be slow.

To be honest, the digital simulation in TINA isn’t that great to begin with, so you’re not missing much. If you want basic digital simulation, check it iCircuit. It costs like $10, but it works on Windows, Mac, iOS and Android, is easy to use and includes a comprehensive library of digital building blocks (it also does basic analog simulation as well). There’s also the free, browser based Falstad Online Circuit Simulator that’s nice for sharing basic ideas with other people.

By the way, did you see the working download link to LTspice IV I found for you? You really should give it a try. Watch some videos on it, play around. http://ltspice.linear-tech.com/software/LTspiceIV.exe

I did follow that link. The download for LTspice IV ends up being LTspice XVII ?? I have already installed LTspice XVII and it hangs up when I run it with error user32.dll. I have a picture of the error. Maybe you can make some sense of it.

[John Heath]

Thank you for a quality post. I can see you are using different analogies hoping one of them will get the point across. I got some of it but not all.
A few questions.

A] 100 amps filtered DC going through a wire. No skin effect zip nada zero. Yes / no ?

None, current density is evenly distributed (according to resistivity and Ohm's law in bulk material).

B] For AC current. Less inductance on the outside , skin , of the wire so more current on the skin . Yes / no?
...
If your answer to A is yes and B is yes is It is mcounter EMF

Is is?

There's always EMF, but tracking the EMF around and within a wire doesn't seem as useful to me.

Inductance isn't the motivating factor here -- it's not like, say, an equivalent circuit where there's a bunch of independent current paths wired in parallel, and current distributes according to their impedances.  It's more like a ladder diagram, where there's two terminals (the external fields at the surface, where you can probe / connect to it), then a chain of alternating series and parallel components (namely, L and R), where the further down the chain you go, corresponds to depth beneath the surface.  Only at DC do the resistors all connect in parallel (X_L = 0), while at higher frequencies, the L's cut off some of the resistance, causing R_AC to rise and concentrating current flow towards the surface.

Tim

Your words are similar to what Wikipedia says. Wikipedia is a reliable source for information so you are in good company ,, most of the time.

https://en.wikipedia.org/wiki/Skin_effect

In the Wikipedia article they give an example of a coax cable and how the skin effect increases with frequency. My anntenna was up as it smacked of a theoretical model prediction not a measurement made. There is a difference between theory and a measurement made. There is a working example where an extreme dc current will cause negative charges moving within to converge to the center. This is a working example used in real life therefore a measurement made not a theoretical model. The working example is called a lithium lens. A 6 cm long round tube of lithium. They shoot anti protons through it. This in itself does not do much however when combined with 500,000 amps of current the negative charges , anti protons , converge to the center thus the name lithium lens to converge the negative anti proton negative charges to a focal point. I trust Wikipedia however when a measurement made is in conflict with Wiki ?. There is a fork in the road. Which path to take   I am on the fence on this one . I will provide a link to a video describing a lithium lens. I would be interested in your take on this. Is it in conflict with Wikipedia for the skin effect ?

https://en.wikipedia.org/wiki/Skin_effect

[John Heath]

I have already installed LTspice XVII and it hangs up when I run it with error user32.dll. I have a picture of the error. Maybe you can make some sense of it.

Touch screen support was introduced long ago, in a crude form. It was not merged to standard libraries (kernel32, user32, gui32, etc.) until Windows 7, so that function was not available in Windows Vista. You need to upgrade to Windows 7 or later.

https://msdn.microsoft.com/en-us/library/windows/desktop/dd371423(v=vs.85).aspx

That's what I like about eevblog. There is always someone that knows. It never fails. Win 7 Hmm. That could be done. I will copy  LTspice XVII instal to a win 7 computer and try.

[T3sl4co1l]

Your words are similar to what Wikipedia says. Wikipedia is a reliable source for information so you are in good company ,, most of the time.

https://en.wikipedia.org/wiki/Skin_effect

In the Wikipedia article they give an example of a coax cable and how the skin effect increases with frequency. My anntenna was up as it smacked of a theoretical model prediction not a measurement made. There is a difference between theory and a measurement made.

Have you tried to measure it?

Have you formulated a problem which would be able to confirm or deny the frequency dependence of skin effect?

A good example is measuring the series resistance component of a straight wire.  Somewhat tricky to do as inductive reactance dominates (above ~10kHz depending on size) but a good exercise in nulling techniques and low impedance measurement.

The reason the theory is so good is because it's been tested.

There is a working example where an extreme dc current will cause negative charges moving within to converge to the center. This is a working example used in real life therefore a measurement made not a theoretical model. The working example is called a lithium lens. A 6 cm long round tube of lithium. They shoot anti protons through it. This in itself does not do much however when combined with 500,000 amps of current the negative charges , anti protons , converge to the center thus the name lithium lens to converge the negative anti proton negative charges to a focal point.

Yeah, so what?

I highlighted the key word here.

Note that they have to maintain that current for tens of microseconds, otherwise the beam will only be focused to (diameter - skin depth) and not the maximal extent.  But they cannot maintain it indefinitely, as the lithium will fuse in a fraction of a second (which would be rather messy in the lab or in the beam line!).

They have to use lithium because it is the first element that is conductive.  Low atomic number --> small cross section to particles.  It's not the most conductive element, so it takes quite a lot of voltage, and energy, to achieve that current.  The rod is about 0.25mohm, so the drop is 127V and power 64MW; a 100us pulse requires 6kJ, probably stored in a somewhat larger electrolytic capacitor bank.  The peak temperature rise will be around 100C, so it won't be destroyed by a short pulse, and can be cooled back to ambient temperature with an outer cooling jacket.  (These figures are around room temperature; it may be cooled to LN2 or even LHe temperatures in the beamline, where conductivity will be even better.)

Anyway, note that electrons are confined to the metal.  The mean thermal energy is about 26meV (at room temperature), well within the conduction band (which, as this is a metal, we know the Fermi level is above the band gap or the band gap is nonexistent, and so there is a ready supply of freely mobile electrons in the material).  The mean drift energy of those electrons, during the pulse, will be, probably fractional meV at best.  That is, thermal energy dominates, and the electrons hardly budge when the pulse happens.  Just offhand, I don't think this is anywhere near enough current to run into current saturation problems -- metals contain a truly massive number of conduction electrons.  It would be an interesting calculation to see where that threshold is (left as an exercise to the student ).

Electrons are not free-as-in-vacuum, which requires 3eV or more.  You would need a truly extreme electric field to achieve that in a bulk metal (or a little UV light shining on the surface).

But what is free-as-in-vacuum?  The antiprotons.  Those are moving, certainly fast enough that they aren't dwelling in the lithium for long enough to annihilate significantly (there will be a fraction lost due to collision, though, and the debris from those collisions will contaminate the beam, and have to be separated -- perhaps by charge/mass separation and some apertures).

This is not a device that you can simply plug in your cooled antiproton gas at one end, and have it bleed out the other side.  No, that would completely annihilate all those hard-won antiprotons!  They must be going very fast indeed, maybe not relativistic but many MeV certainly.  This is well beyond ordinary electrical conduction and steady state thermalized matter, this is hugely concentrated, high energy, high temperature particle physics.

On a related note, the LHC's beam stop (for protons, antiprotons and heavy nuclei, whatever they're shooting that day) is something like two meters of solid graphite.  All two meters are needed.  And the conductivity of graphite is well needed, too (the beam is swirled over the cylinder to better distribute the energy, rather than just ionizing a freaking hole in it ).  A beam of that energy has serious penetration depth!

On that note, I wonder how much beam luminosity and energy can be handled by that lithium lens; at what point does the beam energy loss exceed electrical (conduction) loss?  Hmm...

Tim

[John Heath]

Your words are similar to what Wikipedia says. Wikipedia is a reliable source for information so you are in good company ,, most of the time.

https://en.wikipedia.org/wiki/Skin_effect

In the Wikipedia article they give an example of a coax cable and how the skin effect increases with frequency. My anntenna was up as it smacked of a theoretical model prediction not a measurement made. There is a difference between theory and a measurement made.

Have you tried to measure it?


Have you formulated a problem which would be able to confirm or deny the frequency dependence of skin effect?


A good example is measuring the series resistance component of a straight wire.  Somewhat tricky to do as inductive reactance dominates (above ~10kHz depending on size) but a good exercise in nulling techniques and low impedance measurement.

The reason the theory is so good is because it's been tested.



Newtonian physics has been test and known to be true. At last nature has thrown us a softball so we can proceed forward. Along comes Einstein and oops it was not a softball , it was a hardball. Oliver Heaviside  builds a foundation for all of electronics today that looked like a softball. Along came quantum mechanics and oops it was another hardball.

I did try to measure a magnetic field resulting from the movement of charges and found that ballistic movement of charges and current in a wire are not the same. What looked like a softball turned out to be a hardball. For example how would my magnetic probe using a hall effect know the difference between 2 electrons moving slowly and 1 electron moving quickly. The magnetic probe would see 2 small pulses or 1 big pulse and average that out to be the same. The difference between 1 electron and 2 electrons is not the same current but my magnetic probe thinks they are the same. As a magnetic hall effect probe is known to be true for current then a conclusion is all electrons must be moving at the same speed. To pick a number for that speed c would be a likely candidate. 

It gets worse , a double hardball. If the cloud drift velocity of electrons in current carrying wire is m meter per second then how could all electrons be moving at c ? One way out is for electrons to jump from place to place at c then stay at a hotel over night before trying to jump again at speed c. The problem with this solution is current would start to quantify at vary low currents with most of the lazy electron sleeping in hotels. As it turns out very low currents are quantifying when measured as predicted by quantum mechanics. In summary electron current in a wire is not the same as ballistic movement of charges in a vacuum or lithium in this case.

With all this going on I find it confusing with too many variables on the table. Why are electrons staying obedient to skin effect for a rapidly changing current in the lithium bar and yet the anti protons are not? For one thing the anti proton has a constant net average rate of current , DC ,   but the electrons not. Also the anti proton ballistic speed at .99 c could be is much slower than the electron jumps a .9999 c , less skin effect. I do not have a warm feeling of understanding as there are too many variables on the table. 

Will have to address the latter part of your post separately.

 

[T3sl4co1l]

Big quote

Tim

[Marco]

I don't really understand the point of all this ... knowledge of EM won't allow you to break conservation of energy

[John Heath]

Big quote

Tim

Yes I see your point . I do not have the hang of EEVblog editor yet. I start talking after you say " The reason theory is good is because it has been tested."

[John Heath]

I don't really understand the point of all this ... knowledge of EM won't allow you to break conservation of energy

I admire succinctness however in this case maybe too succinct. Can you put a finger on where you saw a violation to energy conservation laws?

[T3sl4co1l]

Newtonian physics has been test and known to be true. At last nature has thrown us a softball so we can proceed forward. Along comes Einstein and oops it was not a softball , it was a hardball. Oliver Heaviside  builds a foundation for all of electronics today that looked like a softball. Along came quantum mechanics and oops it was another hardball.

But you don't need any of them to understand how to throw a softball.

Only use the model level you need to, no more. Check the higher levels for relevance, keep them in mind for possible gotchas -- but don't use them if you don't have to.

You literally cannot throw a softball in QM, not today without quantum computers at least.  There are too many particles to keep track of, and too little value to be had from it.  The collective motion of 10^24 particles is intractable.  But averaging over those particles to approximate them as a continuous bulk solid, now you can start to do things.  Acoustic waves, momentum transfer; aha, now we can hear the crack of the bat!

If we never touch QM in the first place, that's just as well.  Indeed, there's no way we can average over the materials of a ball and bat today, to determine the average properties of those materials; we're better off measuring it in the first place.  Empiricism wins, here.  (Well, something like an aluminum softball bat is probably solvable from first principles, today.  Maybe a wooden bat too, but then we need to measure the microstructure -- the pores, crosslinking fibers, cellulose crystals and lignin macromolecules -- and things get exponentially harder, and less pure, more empirical.  The ball itself, made from a variety of packed materials, will be similarly difficult.)

Rest assured, even if you invoke QM to solve a classical problem the hard way, it can never give an answer greatly different from what you were already expecting, using [valid] classical methods.  The fancier model always reduces to the classical, under the constraints that apply to the classical model.  (In the case of QM and Relativity vs. Newtonian mechanics, that's v << c, N(particles) >> (a lot) and T >> 0.)

I did try to measure a magnetic field resulting from the movement of charges and found that ballistic movement of charges and current in a wire are not the same. What looked like a softball turned out to be a hardball. For example how would my magnetic probe using a hall effect know the difference between 2 electrons moving slowly and 1 electron moving quickly. The magnetic probe would see 2 small pulses or 1 big pulse and average that out to be the same. The difference between 1 electron and 2 electrons is not the same current but my magnetic probe thinks they are the same. As a magnetic hall effect probe is known to be true for current then a conclusion is all electrons must be moving at the same speed. To pick a number for that speed c would be a likely candidate.

I'd be quite surprised if your Hall effect probe can resolve microamperes, let alone quantized charge!

Riddle: if a resistor in series with a vacuum tube cathode shows a constant current flowing, yet the plate voltage is being toggled between two voltages (say, 1000V and 2000V), what's happening to the electron beam?

(For argument's sake, let's say it's a CRT with a thin neck, so we can clamp a current meter around it, too.)

It gets worse , a double hardball. If the cloud drift velocity of electrons in current carrying wire is m meter per second then how could all electrons be moving at c ? One way out is for electrons to jump from place to place at c then stay at a hotel over night before trying to jump again at speed c. The problem with this solution is current would start to quantify at vary low currents with most of the lazy electron sleeping in hotels. As it turns out very low currents are quantifying when measured as predicted by quantum mechanics. In summary electron current in a wire is not the same as ballistic movement of charges in a vacuum or lithium in this case.

With all this going on I find it confusing with too many variables on the table. Why are electrons staying obedient to skin effect for a rapidly changing current in the lithium bar and yet the anti protons are not? For one thing the anti proton has a constant net average rate of current , DC ,   but the electrons not. Also the anti proton ballistic speed at .99 c could be is much slower than the electron jumps a .9999 c , less skin effect. I do not have a warm feeling of understanding as there are too many variables on the table. 

You're really jumping the shark here!

What assumption is necessary for the classical approximation (bulk conductivity) to hold?

N(particles) >> (a lot).

And I suppose some things about thermal energy, thermalization time and such.  In short, it's a quasi-static equilibrium, as far as the current is concerned.

You don't start to violate that in metals until the high THz, where the conductivity takes on reactance due to electron motion, and eventually (even for single photons) that motion must exceed the plasma frequency or thermal energy in the material (and then you get photoelectric emission and weird quantum stuff like that).

Thus, skin effect is a collective, bulk effect, which breaks down on very small scales and high energies.

Note that it works on the margin, because high energies (i.e. ~optical photons) only interact with the first few layers of a metal anyway (more or less the Debye scattering distance, which is derived from the physics of electrons in a periodic crystal).  The quantum version of skin effect is a parameter like this.

Why doesn't the antiproton beam spread out and conduct through and around the solid, like the cold, obedient electrons do?  Because there's nothing to stop it and move it around such a path.  It feels its own field (self interaction), and it feels the field from the current flow, but at the velocity it's going, the cross section for particle interactions is pretty small.  The relative momentum of any pair of particles (lithium nuclei and antiprotons, electrons and antiprotons) is way in the non-bonding range, so they certainly won't just snap in line and spread out.  With a relativistic velocity (if they're that fast, I don't know), length contraction further reduces the cross section, giving low beam loss.

The current from the beam is very small in relation to the total current, but it too has a magnetic field; that field is trapped within the lithium cylinder, just as you would expect.  It will act as a tiny line-like current through the solid, not carried through the solid as a classical ohmic conductor (and so, there's no equivalent circuit between the cylinder's resistance, and external supply, and the beam), but nonetheless present, and its field will be shielded by the surrounding conductor according to the response you would expect.  (Namely: presumably the antiprotons are in bunches, so that the skin depth will be very shallow, microns maybe.  By the way, this has the convenient feature of shorting out most of the magnetic field of the beam, keeping it small, making the focusing that much more effective, I think?)

This is an example of a problem where a mixed, semi-classical solution is possible (and necessary!).  There's nothing wrong with using classical results in non-classical physics, as long as the assumptions remain correct -- QM happily uses the Coulomb formula to calculate energy potentials, for example.  (Now, QED underlies EM & QM, but you don't need to invoke that except for very precise atom and particle interactions.)

Tim

[Marco]

Your original theory of the heatless resistor, if the supply is providing power it either needs to go into heat or some kind of storage medium. You lacked a storage medium, hence you're trying to break conservation of energy.

I was wrong to suggest a simulator. It's better to just run it through in your head.

- The current in the inductor will be a symmetrical triangle wave, possibly with some DC bias due to the way it started up.
- The supply would see that wave, but with every other half of it negated (including the DC bias).
- Draw it out in your head or on paper and determine the average current the supply sees.

Hint, it's zero. The power supply is delivering no energy. Your circuit is simulating an infinite resistor, which indeed doesn't get hot ... but isn't very useful.

[John Heath]

Your original theory of the heatless resistor, if the supply is providing power it either needs to go into heat or some kind of storage medium. You lacked a storage medium, hence you're trying to break conservation of energy.

I was wrong to suggest a simulator. It's better to just run it through in your head.

- The current in the inductor will be a symmetrical triangle wave, possibly with some DC bias due to the way it started up.
- The supply would see that wave, but with every other half of it negated (including the DC bias).
- Draw it out in your head or on paper and determine the average current the supply sees.

Hint, it's zero. The power supply is delivering no energy. Your circuit is simulating an infinite resistor, which indeed doesn't get hot ... but isn't very useful.

We all have our own way of stewing on a problem. For myself it is usually using Newtonian analogies then pacing the floor for a few nights before any prototyping of ICs on a board. Most of the time the floor pacing has already sorted out what ICs , transistors will be used and how it will look.

Back to your point. I have a light bulb 1 volt , 1 watt and a power supply 1 volt. When connected 1 amp will go through to light bulb for 1 watt. I want to dim the light to 1/2. I will switch the light on and off with a 50 percent duty cycle. Now my l watt light is only on for 50 percent of the time so the average wattage is only 1/2 watt not 1 watt. This is how a dimmer switch works with triacs to dim lights in a house.

The idea presented here in this thread is to use an inductor instead of a triac to vary wattage by switching the polarity of the inductor. Theoretically it will work but is it practical ? Is there a market for it ?
 You are a 100 percent correct that there can not be a heatless resistor without violating energy conservation laws. However an inductor is not a resistor , more like a flywheel where energy can be shifted in time.   

[Marco]

60 Hz is pretty much DC in this case.

Think of your circuit as a black box for a moment. It has a load below and a power supply up top, if it was passing a "DC current" to the load with a DC voltage drop, it would by necessity be absorbing power. V*I will not be denied. If it acts like a resistor it burns power or stores it, no way around.

Which is why it actually has an infinite DC resistance, it doesn"t get hot because it passes no current. Simply chopping the input voltage through an inductor works of course, but then it's a simple buck.

[John Heath]

Newtonian physics has been test and known to be true. At last nature has thrown us a softball so we can proceed forward. Along comes Einstein and oops it was not a softball , it was a hardball. Oliver Heaviside  builds a foundation for all of electronics today that looked like a softball. Along came quantum mechanics and oops it was another hardball.

But you don't need any of them to understand how to throw a softball.

Only use the model level you need to, no more. Check the higher levels for relevance, keep them in mind for possible gotchas -- but don't use them if you don't have to.

You literally cannot throw a softball in QM, not today without quantum computers at least.  There are too many particles to keep track of, and too little value to be had from it.  The collective motion of 10^24 particles is intractable.  But averaging over those particles to approximate them as a continuous bulk solid, now you can start to do things.  Acoustic waves, momentum transfer; aha, now we can hear the crack of the bat!

If we never touch QM in the first place, that's just as well.  Indeed, there's no way we can average over the materials of a ball and bat today, to determine the average properties of those materials; we're better off measuring it in the first place.  Empiricism wins, here.  (Well, something like an aluminum softball bat is probably solvable from first principles, today.  Maybe a wooden bat too, but then we need to measure the microstructure -- the pores, crosslinking fibers, cellulose crystals and lignin macromolecules -- and things get exponentially harder, and less pure, more empirical.  The ball itself, made from a variety of packed materials, will be similarly difficult.)

Rest assured, even if you invoke QM to solve a classical problem the hard way, it can never give an answer greatly different from what you were already expecting, using [valid] classical methods.  The fancier model always reduces to the classical, under the constraints that apply to the classical model.  (In the case of QM and Relativity vs. Newtonian mechanics, that's v << c, N(particles) >> (a lot) and T >> 0.)

I agree. I used the softball approach to navigate through problems. However when work is done and the rent is payed you can not help but think of the hardball problems.

I'd be quite surprised if your Hall effect probe can resolve microamperes, let alone quantized charge!

Riddle: if a resistor in series with a vacuum tube cathode shows a constant current flowing, yet the plate voltage is being toggled between two voltages (say, 1000V and 2000V), what's happening to the electron beam?

(For argument's sake, let's say it's a CRT with a thin neck, so we can clamp a current meter around it, too.)

My 50 dollar RMS open ended current probe is good for .1 amps on a good day. Micro amps is not going to happen. In large print it says RMS but in small print it says RMS providing you are measuring a sine wave , ha. God bless the creative minds in marketing.

Your CRT analogy is working. I set it to constant current at 1 m amp then put my magic 1 m amp clamp meter around the neck. After pacing the floor for a bit I can see your point. For both 1000 and 2000 volts the magnetic field is the same so the magnetic meter will read 1 m amp in both cases. Slow but dense beam of electrons vs fast but less dense beam of electrons. The conclusion is a magnetic current meter will work the same for current in a wire as well as ballistic movement of charges. Disregard my 1 fast vs 2 slow electron problem as it appears to be false.

You're really jumping the shark here!

What assumption is necessary for the classical approximation (bulk conductivity) to hold?

N(particles) >> (a lot).

And I suppose some things about thermal energy, thermalization time and such.  In short, it's a quasi-static equilibrium, as far as the current is concerned.

You don't start to violate that in metals until the high THz, where the conductivity takes on reactance due to electron motion, and eventually (even for single photons) that motion must exceed the plasma frequency or thermal energy in the material (and then you get photoelectric emission and weird quantum stuff like that).

I would put electron mass starting to contribute to inductance in the THz range as a softball. It has charge inertia and it has its mass inertia as well.   

The quantifying of an EM wave into photons of energy h times frequency is a bit of a hardball. The photoelectric effect is true and repeatable so it can not be denied. I believe there is a way to trap a photon to have a closer look at it. A nice fat photon 3 feet in diameter. Will set up a wire 10 feet long and drive it with a 100 MHz RF source to have a resonate standing wave on the ten foot wire. Now we have big fat 3 foot photons trapped on our wire with no way out. If you walk down this wire with a fluorescent bulb you can see where the electric fields peak and it looks like a sine wave. If you walk down the wire with a current meter you can see the magnetic field of the photon that is also a sine wave and out of phase with the electric field . Wikidedia has a few definitions of a photon depending on who's opinion. A photon trapped in a standing wave on a wire is a measurement made not an opinion. It says that a photon is not length contracted and that the electric and magnetic fields are out of phase. I would be interested in knowing if you are buying this or maybe no it is not the same as a photon.
[quote/]

[John Heath]

eebblog says I can modify a give post. That means I can go back in time and fix mistakes. So if anyone reads this post you are delusional as this post never happened in the new time line I will create by modifying and correcting mistakes made in the post in the past.  Now I am getting the hang of eevblog editor.

[John Heath]

Your original theory of the heatless resistor, if the supply is providing power it either needs to go into heat or some kind of storage medium. You lacked a storage medium, hence you're trying to break conservation of energy.

I was wrong to suggest a simulator. It's better to just run it through in your head.

- The current in the inductor will be a symmetrical triangle wave, possibly with some DC bias due to the way it started up.
- The supply would see that wave, but with every other half of it negated (including the DC bias).
- Draw it out in your head or on paper and determine the average current the supply sees.

Hint, it's zero. The power supply is delivering no energy. Your circuit is simulating an infinite resistor, which indeed doesn't get hot ... but isn't very useful.

You can get a lot of milage out of I*V=watt. However when it comes to AC reactance has to be considered. I have a video link that describes it better than I would.

[Marco]

The AC reactance is neither here nor there, you want it to conduct a "DC current" ... it won't.

[T3sl4co1l]

Give that editing another go, it looks like you got the quote tags reversed??

Tim

[John Heath]

Where are my ICs in the Tina9 software? I see a 555 timer and an op-amp. Where is the 4000 series and 74hc series of ICs. Do I have to down load these separately?

These type of SPICE simulators are primarily for doing analog simulation, not digital. (Not to say you can’t; I know there are limited sets of 4000 and 74 series models for LTspice, for example, but these type of packages don’t excel pure at digital simulation, since they will be simulating the analog characteristics of each transistor and FET of the part.)

You should also know that SPICE simulators like this aren’t intended to simulate an entire large circuit in a single go. You’re meant to break it up into smaller chunks. (If you need to use the output of one chunk as the input of another, you can save the output as a waveform (PWL file) and then use it as an input later.)

Anyway, based on your OP we thought you needed a good analog simulator. If you want to do fast digital simulation we can recommend some software for that.o

I was looking at some more videos on Tina. Apparently there are Tinas and there are TINAS . I took a picture off the videos so you can see the difference between Tina and TINA TINA gets optoelectronics , your choice of logic ICs , a bunch of MCUs , A/D D/A converters , the list go on and on. What did I get in the "Tina package" one stinking 555 timer ?  What am I supposed to do with that blink a  LED on and off? What am I chicken liver here? Why does TINA get all the good stuff while I am stuck with one stinking 555 timer? Pardon the humor as I need the practice. I am sure it is a Tina library add on. Just wondering where to find this Tina library add on for those MPUs and such?

The full version of TINA is a commercial package and costs several hundred dollars to start. However, TI offers models that will work in their cut down version of TINA. Also, most other standard Berkeley SPICE models will work, but these are full analog simulations of the digital parts, so it will be slow.

To be honest, the digital simulation in TINA isn’t that great to begin with, so you’re not missing much. If you want basic digital simulation, check it iCircuit. It costs like $10, but it works on Windows, Mac, iOS and Android, is easy to use and includes a comprehensive library of digital building blocks (it also does basic analog simulation as well). There’s also the free, browser based Falstad Online Circuit Simulator that’s nice for sharing basic ideas with other people.

By the way, did you see the working download link to LTspice IV I found for you? You really should give it a try. Watch some videos on it, play around. http://ltspice.linear-tech.com/software/LTspiceIV.exe

I manage to build the cold resistor in Tina. It is not Tina Turner as it takes about 20 minutes to work up the transient simulation. Is there a way to speed it up a bit?

[John Heath]

The cold resistor appears to work according to a Tina simulator. A 10 m Henry inductor switching it's polarity 10 time a second with 10 volts applied to it. Not sure what it's net average resistance would be as it is both charging and discharging the 10 volt source?

[T3sl4co1l]

Relays are a very strange component choice, for several reasons...

Is that not shorted to ground on one side?

Tim