@@copernicofelinis I watched all your videos on the torriod puzzle, all the time trying to rationalise what was happening. You seem to have the theory and the maths, but my take on the effect is more pragmatic:. If you omitted the resistors and kept the two digital volt meters, the meters and their leads would make one turn of the torriod. Each meter would comprise half of the turn, and assuming the DVMs had identical resistance there would be identical voltages across each. Introducing a 'shunt' resistor across one meter would cause that meter to read lower than it did originally as current is diverted away from it. The other meter could then be shunted with a different value resistor and its value would also be lower than the original. Perhaps a bit too pragmatic? But I just loved the way you made it a mystery! It really held my attention. Many many thanks to you. Richard.
@@richardlangner it is pragmatic, and it can be used to find the voltages, but there are some subtleties that need to be considered. One: you say "voltage across" the half turns, but since voltage is path dependent you should specify a path. If the path is along the half turn, then voltage along it is nearly zero. In fact, when you place the two voltmeters around the core, you end up with all the voltage to drop on the internal resistors - none has been left in the leads and probes. I found out that the best way to explain voltmeter readings is by introducing the concept of measurement loop, i.e. the loop formed by voltmeter, leads, and the branch of circuit you are interested in (there may be several, connected to the same two endpoints). If the measurement loop for branch X does not include any relevant changing magnetic field, then the voltmeter reads the correct branch voltage. If the measurement loop for branch Y (attached to the same points as branch X!) links some dB/dt, then you need to correct the reading by discounting the linked emf. I have already completed the scripts for two upcoming videos on "What a voltmeter reads" and "How a voltmeter measures what it measures", that will be published after the "IEC voltage" video. (I am temporarily stopped because I destroyed my good phone, so I have no device to record the voiceover with decent quality). The shunting effect you describe is correct, and I will address it in the circuital treatment of the Lewin ring (some of it is in one of my answers on EE Stack Exchange, but I can't give a link because yt will delete it).
Here from Silicon Soup. Oh, the great Kirchhoff is for the birds debate which perplexed me much and then the internet formed well intentioned camps on both sides. "The Mystery of the Lewin Clock" by Treavor Kearney (high level analysis) here on You Tube was posted a couple days ago. Thanks for your contribution as I found it helpful.
Thank you for pointing out the new video by Trevor. It seems he, SiliconSoup and I have 'specialized' in covering different angles of the Lewin ring: Trevor is more focused on areas and geometry, SiliconSoup on charge density, while I prefer to look at fields and measurement loops (this last part will be clear when I'll upload the "What a voltmeter measures" video.)
Hi Copernico Concerning why the voltmeters give the correct readings for the resistor voltages. The resistor leads are in the induced electric field and the voltage for the resistors is the sum of induced electric field and the Coulomb field. The voltmeter leads are also in the induced electric field and the voltmeters display the sum of the voltages from the induced electric field along the voltmeter leads combined with the potential difference from the Coulomb field created by the resistance of the resistors.
Each voltmeter shows the line integral of the TOTAL electric field along the path that goes through its probes and its internal resistor. This voltage is the same as the voltage along the tested branch of circuit only if there is no changing magnetic field linked. Each voltmeter is connected to both branches of the circuit: one branch will form a loop with the probes that does not link the core, the other will form a loop that does link the core. The voltage shown by the voltmeter will be equal to the voltage along the branch that does not form a loop around the core. All of this will be shown in the next video. What is important to notice here is that the field is a composition of two components and that this resultant is almost zero inside the conductor portions of the ring (in accordance with Ohm's law).
@@copernicofelinis The low resistance only reduces the Coulomb component along the conductor, it does not reduce the Faraday electric field along the conductor.
@@woodcoast5026 no. The coulombian component is almost equal to the induced component . They are both around 1.1V/m, their difference is the negligible 0.0002 V/m that is compatible with the high conductivity of copper. The coulombian electric field (almost completely) obliterates the induced electric field in the conductor.
@@copernicofelinis That does not "obliterate" the Faraday field.The Faraday field is still there. The two components are still there forming the two components of the composition .
@@woodcoast5026 yes, that is correct, but the operation of superposition is something that resides in our heads only. What atoms and electrons 'see' and 'feel' is just the resultant field which is nearly zero. And it is nearly zero because the coulombian field has nearly almost entirely canceled the induced field in the copper. The same happens in the electrostatic case: the electrostatic field in a conductor is exactly zero because the external field has been obliterated by the field component generated by the displaced surface charge. Even more interesting: the interior of the conductor *never* gets a chance to 'see' or 'feel' the external field, because the surface charge kills it before it can penetrate the conductor.
"Probing has nothing to do with the voltages being different." As several other people had previously shown - Lewin was completely wrong and it is entirely due to his inadequate sloppy measurement setup. It is not even a hard setup to get right. ua-cam.com/video/JpVoT101Azg/v-deo.html
I am well aware of these "probing done right" videos, and what they try to recover is the path integral of the coulombian electric field alone (the middle picture in the diagram with three rings). This is the conservative **part** of the electric field that admits a scalar electric potential. The problem with this approach is threefold: 1. It describes only "half" of the physical system: one should also give the vector potential A to give the complete picture. 2. It forces you to consider a different physics for loops that link a variable flux and loops that do not, making the physics schizophrenic. In particular one has to invent reasons for the failure of Ohm's law inside every coil. 3. Voltmeters measure the difference on voltage, not the difference in electric potential; it is only in the conservative case that these two quantities coincide. I will show this in the next video. So, no, that is not good probing because they put their probes in the middle of the changing magnetic flux region, and because the quantity they recover tells only half of the story.
@@copernicofelinis "It describes only "half" of the physical system:" No, they simply are measuring correctly. "It forces you to consider a different physics for loops that link a variable flux and loops that do not" That is not the case either - they simply show how to measure correctly. "Voltmeters measure the difference on voltage, not the difference in electric potential" Aaaaaannnddd you might want to refresh your memory on that one - the definition of voltage for example - cause that IS the difference in electrical potential. You have not addressed anything but instead are making up ridiculous claims. By now it seems more like you subsrcibed the a false notion of physics and are now becoming more and more reluctant to accept that you were wrong, to the point of throwing a tantrum.
@@ABaumstumpf let's see: what is the potential difference between point A and the top terminal of the smallest resistor, according to Mabilde? How many volts? And what is the resistance of the copper conductor for that same path? Show me how Ohm's law work in this case.
@@copernicofelinis "Show me how Ohm's law work in this case." You are the one making the false claims. You are claiming that the most well known theories of electrondynamics are wrong - the burden of proof is on you. What Mabilde has down was simply showing that Lewin had an error in his measuring-setup and if corrected all his spurious claims fall apart. And now you are getting emotional cause you made the same mistake.
@@ABaumstumpf what setup? Look at the diagrams of the two half circuits where I show the computation of voltage as E x length. There are NO PROBES. The reason the voltmeters in the video show the correct values as computed from first principles is because the probing there is correct. But the values of those voltages are computed without the need of any probes. Oh, BTW, Ohm's law works perfectly fine with my values of voltage. No need to invent a different physics. Mine is the physics taught at Berkeley and MIT. ( Invoking the authority principle is a good thing in a UA-cam video because it allows viewers to know that what they see is not some 'original research' but is at least based on real science).
Thanks, you do some interesting stuff, and explain it in a relaxed way.
Thank you for your feedback.
And for your interesting videos.
@@copernicofelinis
I watched all your videos on the torriod puzzle, all the time trying to rationalise what was happening. You seem to have the theory and the maths, but my take on the effect is more pragmatic:.
If you omitted the resistors and kept the two digital volt meters, the meters and their leads would make one turn of the torriod. Each meter would comprise half of the turn, and assuming the DVMs had identical resistance there would be identical voltages across each. Introducing a 'shunt' resistor across one meter would cause that meter to read lower than it did originally as current is diverted away from it. The other meter could then be shunted with a different value resistor and its value would also be lower than the original.
Perhaps a bit too pragmatic?
But I just loved the way you made it a mystery! It really held my attention. Many many thanks to you.
Richard.
@@richardlangner it is pragmatic, and it can be used to find the voltages, but there are some subtleties that need to be considered.
One: you say "voltage across" the half turns, but since voltage is path dependent you should specify a path. If the path is along the half turn, then voltage along it is nearly zero. In fact, when you place the two voltmeters around the core, you end up with all the voltage to drop on the internal resistors - none has been left in the leads and probes.
I found out that the best way to explain voltmeter readings is by introducing the concept of measurement loop, i.e. the loop formed by voltmeter, leads, and the branch of circuit you are interested in (there may be several, connected to the same two endpoints). If the measurement loop for branch X does not include any relevant changing magnetic field, then the voltmeter reads the correct branch voltage. If the measurement loop for branch Y (attached to the same points as branch X!) links some dB/dt, then you need to correct the reading by discounting the linked emf.
I have already completed the scripts for two upcoming videos on "What a voltmeter reads" and "How a voltmeter measures what it measures", that will be published after the "IEC voltage" video. (I am temporarily stopped because I destroyed my good phone, so I have no device to record the voiceover with decent quality).
The shunting effect you describe is correct, and I will address it in the circuital treatment of the Lewin ring (some of it is in one of my answers on EE Stack Exchange, but I can't give a link because yt will delete it).
Here from Silicon Soup. Oh, the great Kirchhoff is for the birds debate which perplexed me much and then the internet formed well intentioned camps on both sides. "The Mystery of the Lewin Clock" by Treavor Kearney (high level analysis) here on You Tube was posted a couple days ago. Thanks for your contribution as I found it helpful.
Thank you for pointing out the new video by Trevor. It seems he, SiliconSoup and I have 'specialized' in covering different angles of the Lewin ring: Trevor is more focused on areas and geometry, SiliconSoup on charge density, while I prefer to look at fields and measurement loops (this last part will be clear when I'll upload the "What a voltmeter measures" video.)
Hi Copernico
Concerning why the voltmeters give the correct readings for the resistor voltages.
The resistor leads are in the induced electric field and the voltage for the resistors is the sum of induced electric field and the Coulomb field. The voltmeter leads are also in the induced electric field and the voltmeters display the sum of the voltages from the induced electric field along the voltmeter leads combined with the potential difference from the Coulomb field created by the resistance of the resistors.
Each voltmeter shows the line integral of the TOTAL electric field along the path that goes through its probes and its internal resistor. This voltage is the same as the voltage along the tested branch of circuit only if there is no changing magnetic field linked. Each voltmeter is connected to both branches of the circuit: one branch will form a loop with the probes that does not link the core, the other will form a loop that does link the core. The voltage shown by the voltmeter will be equal to the voltage along the branch that does not form a loop around the core.
All of this will be shown in the next video. What is important to notice here is that the field is a composition of two components and that this resultant is almost zero inside the conductor portions of the ring (in accordance with Ohm's law).
@@copernicofelinis
The low resistance only reduces the Coulomb component along the conductor, it does not reduce the Faraday electric field along the conductor.
@@woodcoast5026 no. The coulombian component is almost equal to the induced component . They are both around 1.1V/m, their difference is the negligible 0.0002 V/m that is compatible with the high conductivity of copper.
The coulombian electric field (almost completely) obliterates the induced electric field in the conductor.
@@copernicofelinis That does not "obliterate" the Faraday field.The Faraday field is still there. The two components are still there forming the two components of the composition .
@@woodcoast5026 yes, that is correct, but the operation of superposition is something that resides in our heads only. What atoms and electrons 'see' and 'feel' is just the resultant field which is nearly zero. And it is nearly zero because the coulombian field has nearly almost entirely canceled the induced field in the copper.
The same happens in the electrostatic case: the electrostatic field in a conductor is exactly zero because the external field has been obliterated by the field component generated by the displaced surface charge. Even more interesting: the interior of the conductor *never* gets a chance to 'see' or 'feel' the external field, because the surface charge kills it before it can penetrate the conductor.
This genius
Minor language point: one usually says "deceptively simple".
Thank you. I appreciate corrections. Apologies for mauling your language. 😁
@@copernicofelinis No worries! 🙂
"Probing has nothing to do with the voltages being different."
As several other people had previously shown - Lewin was completely wrong and it is entirely due to his inadequate sloppy measurement setup. It is not even a hard setup to get right.
ua-cam.com/video/JpVoT101Azg/v-deo.html
I am well aware of these "probing done right" videos, and what they try to recover is the path integral of the coulombian electric field alone (the middle picture in the diagram with three rings). This is the conservative **part** of the electric field that admits a scalar electric potential. The problem with this approach is threefold:
1. It describes only "half" of the physical system: one should also give the vector potential A to give the complete picture.
2. It forces you to consider a different physics for loops that link a variable flux and loops that do not, making the physics schizophrenic. In particular one has to invent reasons for the failure of Ohm's law inside every coil.
3. Voltmeters measure the difference on voltage, not the difference in electric potential; it is only in the conservative case that these two quantities coincide. I will show this in the next video.
So, no, that is not good probing because they put their probes in the middle of the changing magnetic flux region, and because the quantity they recover tells only half of the story.
@@copernicofelinis "It describes only "half" of the physical system:"
No, they simply are measuring correctly.
"It forces you to consider a different physics for loops that link a variable flux and loops that do not"
That is not the case either - they simply show how to measure correctly.
"Voltmeters measure the difference on voltage, not the difference in electric potential"
Aaaaaannnddd you might want to refresh your memory on that one - the definition of voltage for example - cause that IS the difference in electrical potential.
You have not addressed anything but instead are making up ridiculous claims. By now it seems more like you subsrcibed the a false notion of physics and are now becoming more and more reluctant to accept that you were wrong, to the point of throwing a tantrum.
@@ABaumstumpf let's see: what is the potential difference between point A and the top terminal of the smallest resistor, according to Mabilde? How many volts? And what is the resistance of the copper conductor for that same path?
Show me how Ohm's law work in this case.
@@copernicofelinis "Show me how Ohm's law work in this case."
You are the one making the false claims. You are claiming that the most well known theories of electrondynamics are wrong - the burden of proof is on you.
What Mabilde has down was simply showing that Lewin had an error in his measuring-setup and if corrected all his spurious claims fall apart. And now you are getting emotional cause you made the same mistake.
@@ABaumstumpf what setup? Look at the diagrams of the two half circuits where I show the computation of voltage as E x length. There are NO PROBES.
The reason the voltmeters in the video show the correct values as computed from first principles is because the probing there is correct. But the values of those voltages are computed without the need of any probes.
Oh, BTW, Ohm's law works perfectly fine with my values of voltage. No need to invent a different physics. Mine is the physics taught at Berkeley and MIT. ( Invoking the authority principle is a good thing in a UA-cam video because it allows viewers to know that what they see is not some 'original research' but is at least based on real science).