Does Kirchhoff’s Law Hold? Disagreeing with a Master

hi making this video makes me nervous this is a serious and complex video about an electronic topic and I have to do it very carefully see it’s like you disagree with Stephen Hawking who’s likely wrong you are and now I’m about to disagree with dr. Walter Lewin if you don’t know dr. Levine he has a PhD in physics he’s a former professor of physics at the Massachusetts Institute of Technology or MIT he has made many discoveries has written tons of books has received many awards for his scientific achievements has educated thousands in schools and millions over the web through his online lectures just check his Wikipedia page I on the other hand have a master’s degree in electronics have worked for a while as an engineer and then turned youtuber where I constantly get shocked my mom thinks I’m mostly okay dr. Levine teaches in one of his courses that the Kirchhoff’s voltage law or KVL doesn’t hold true in some cases and I disagree with him the rectifier I tried to contact up to the Winn to discuss this but understandably he doesn’t want to talk about it anymore because so many people online have annoyed him with their stupid reasonings so I humbly make this video hoping that he or some other great profits overseas it and tells me what they think about my results if he’s right more power to him I couldn’t be happier to be wrong and learned something new now what’s Kirchhoff’s voltage law or KVL I read the definition from Wikipedia as my alibi which is the principle of conservation of energy implies that the directed some of the electrical potential differences or voltage around any closed network is zero this is also my understanding and how I learned it if you find any closed loop in your circuit the sum of the voltages across its components at a given time is zero adding them up in one direction this has never failed me what dr. Levin says KVL doesn’t hold when there is a changing magnetic field involved in a circuit the potential difference between two points in a circuit is no longer defined where we have to voltmeters connected to exactly the same two points can measure different values I leave links to his relative lectures in the description and I suggest you watch them but let me quickly summarize his reasoning imagine we have a circuit like this a 1 volt supply in series with a hundred ohm and nine hundred ohm so one volt divided by 1 kilo ohm total means there is a one milliamp running through the loop or point one volt here and point nine volt there if we calculate KVL in the loop in this direction entering positive of r1 we have plus point one volt and entering positive of r2 we have plus point nine volts and entering negative of the supply we have minus 1 volt and the sum of all these is zero Kirchhoff’s law holds fine here but let’s remove the supply and short it and instead apply a changing magnetic field through the loop coming out of the page we know that a changing magnetic field creates current in a loop and according to the Lenz law the direction of the current is this way let’s say at a moment in time the current reaches one milliamp which means we will have point one volt across r1 and point nine volts across r2 the sum of the voltages in the loop is not zero so dr. lloween concludes so clear office for the birds and fire day is not then dr. Levin does an interesting experiment to prove this he measures across the exact same two points in the circuit with two different scopes at the same time and shows that each scope shows a different number three two one zero look on the left there is v1 notice it’s negative look on the right there’s v2 it’s about nine times larger than v1 he then concludes that in this special case depending on which way you look at the circuit you read a different voltage so this half of the circuit has a different voltage than the other half which contradicts the Kirchhoff’s voltage law and it doesn’t hold he then says that it’s the Faraday’s law that always holds not the Kirchhoff’s law which is just a special case of Faraday’s law dr. Levin says that the two points across the wires are electrically are identical spend and appreciate that a one and A two from an electrical point of view identical machine because the resistance of the wire is extremely small compared to the resistors which is true and also the inductance of the wire is extremely small which is also true so the changing current through the wire creates very negligible voltage across the wire if anything I repeated the same test and I agree with his measurements but not his conclusions let me repeat the test for you like dr. Levine I have a coil or solenoid and I’ll switch a battery through a 1 ohm resistor over my coil the resistor limits the current to 10 to 12 amps the coil creates a rise of changing magnetic fields and settles and then I have my loop with 1 kilo ohm resistor on one side and 10 kilo ohm on the other side we can agree the wire resistance and inductance between them is negligible compared to the resistor values so when I apply voltage in my coil the magnetic field in it changes like this and settles the electro-motive force or voltage induced in my loop is the rate of change of magnetic flux and so the induced voltage changes like this now I’ll measure across these two points in the loop using my sense wire that connects to the scope notice that I’ve twisted the sense wire having twisted wire is important because say we have magnetic fields coming out of the board the induced current in the first twisted loop is in this direction and in the next loop is also the same direction this means that say in the black wire the current wants to go in this direction in loop 1 and in this direction in loop 2 and they cancel each other so using twisted pairs make sure that the voltage and current in the wires are not affected by external fields connecting the scope doesn’t affect the main loop behavior at all because it has a hundred mega ohm input impedance so we can safely say there is no loading effect from connecting the scope to the loop where we measure now the sense wires are on the 10 kilo ohm side ready click see I have a voltage pulse with a peak of around 25 millivolts now all I do is I flip the sense wires to the one kilo ohm side of the loop ready hell lick there we have a negative pulse around one tenth of the first balls because although the current in the loop is the same the resistance is one tenth what does it mean we are reading two different voltages across the same spot maybe there is voltage across these wires unlike what we thought I move the sense wires across the loop wire let’s measure kill it huh this scope just triggers a noise there is no voltage across the wires so does it mean that two different voltages from two resistors are applied across the same spot and the Kirchhoff’s law doesn’t hold I’m sorry but this is where dr. Levine and I part ways please don’t hit me wait we are not back in all here on you can’t hit me can you let me show you dr. Levin’s theory is not dependent on the location of the resistors so let’s rearrange them here I move the resistors side by side and very close if I measure across these two points I still read two different voltages depending on which side I do the measurement same as before here I have both my resistors on one side and I’m measuring across these two points on the 10 kilo ohm side there we go Cal lik C we see a pulse around the same size now I flip the wire to the 1 kilo ohm side and kill lik see I see the same 1/10 pulse like before so nothing’s changed there but instead let’s measure right across r1 and r2 and both R 1 and R 2 with minimal localized sensing loops here’s the voltage across the 10k BAM see it’s around at the same 25 millivolts and the voltage across the 1k the same two and a half minutes and the voltage across both resistors PM see it’s actually higher than 25 millivolts pretty close to 27 and a half so you see that the voltage across both r1 and r2 is equal to the voltage across R 1 plus the voltage across r2 which is the same voltage across the loop this shows that the voltage across the loop is not zero unlike what we thought what is equal to vr 1 plus VR 2 the loop is the secondary of a transformer with the primary being my coil dr. Bevin’s model misses a transformer in the loop with the voltage across the winding equal to VR 1 plus VR 2 KVL holds but then dr. Lewin would say you stupid kid well he wouldn’t say that he’s a nice guy what he would say if instead of measuring locally like this we measure across the loop on the other side we would read zero walls across the loop which is correct so which one is right well let me show you an extreme case let’s assume our resistors are infinite or open and so there is no current running through the loop now if we measure the voltage across this tiny gap on this side we see a voltage pulse here’s the loop with no resistors measuring right across the gap and we have a voltage pulse and when we move the sense wires around like this we see zero jump and here I have the same loop with the sense lines running right on top of the loop and we have no voltage jump just some noise of course if I make the sense lines a little bit smaller or larger than the main loop I’ll have voltage jumps so if in fact we have a voltage V across this gap for reference say zero volt here and plus V on this side why do we read zero volts across the sense lines let’s take half way through the loop if the voltage here is plus V the voltage here would be half of e so we have half a V across this half of the loop and another half of V across the other half there is no current running through the sense lines so it doesn’t matter that they are going to the scope both the sense lines and the loop have the same shape and are in the same field so they behave the same which means we have half of e on this sense line and another half of e on the other sense line so if the voltage of the loop on this terminal is V it is reduced on the sense line by half a V here and on the zero terminal it is increased by half a V here so you see that the voltage difference between the sense lines is zero at this point and the scope shows zero so the entire reason dr. Levine was reading two different voltages was due to bad probing no matter where you your circuit the voltage across these two points is always a unique number the voltage on this half of the circuit is the same as the other half well this looks a bit complicated but if you look at this half of the circuit the voltage across this half is v1 which is the voltage across this piece of loop wire plus the resistor voltage which is VR 1 plus V 2 of this piece of wire now if you sense it like this the same voltages of the loop wires are induced on the sense lines which subtract from the voltage across these points and all you read that the scope is VR 1 and if you sense on the other side the induced voltages on the sense lines change to match that side and you read VR 2 now you might say this is different than my extreme case because there is current running through the loop what according to the Lenz law this current actually reduces the original field so the induced voltage on the sense lines is less and they end up matching there were never two different voltages across these points this emphasizes the importance of proper probing now I’m not 100% sure but if my quick analysis is correct to measure the voltage across say these two points properly the sense lines must come straight to gether and twist all the way to the scope or meter and keep your scope probe away – because even if this loop is closed to your fields voltage is induced in it and will affect your readings my conclusion Kirchhoff’s laws hold and have held nicely for me so far if you see any discrepancy it’s because you’re either missing a component in your model or probing wrong have I been wrong before well yeah just look at my previous videos am I wrong now I don’t think so because science and analysis and experiments support my claim as well as a bunch of text books written by smarter people the sad part is that almost all college physics book Halliday interesting Jim : oh hey Neil Young and Freeman they all when they do with self in doctors with solenoids they all say let us now use case of loop rule that statement is a crime well either way I’m sure the science will win think about this gives it some thought is not easy and have a good weekend

100 thoughts on “Does Kirchhoff’s Law Hold? Disagreeing with a Master”

  1. Nit picking Ohm's law, or Kirchhoff is a useless waste of time. I fully understand that there are many electrical elements that do not satisfy ohm's law, batteries and diodes are examples. Kirchhoff and Ohm's laws are empirical relationships. "Any" material will become conductive with a strong enough electrical field acting on it and any conductive material can become non conductive with a strong enough magnetic field..ex..the resistance will increase in proportion to the square of the magnetic field. Don't anyone talk to me about this..This goes beyond the scope of an EE. This is an area that a physicist works in not an EE. Walter Lewin is a Astrophysicist. This is Lewin's area of expertise. To any home electrical enthusiast ..Please don't try to teach me electrical theory. I'm here to relax and perhaps be entertained with pleasant conversation. I know there are other EE's here that are just keeping quiet under the radar (and I'm going to join them). Oh..and be safe with electricity. You only have one life. Let's all try to be respectful and nice.

  2. Magnetic drag would explain these results. Like in the case of an electric motor; if you have two of the same fans, one moving faster than the other connected via a tube: the faster fan will experience drag from the slower fan. Or, if you try to spin an electric motor faster than it is moving, it will give a resistance to the extra movement that will be converted into electrical energy in the circuit. Thusly in the case that you have presented in this video, the voltage will not be constant. The strength of the magnetic field can not be evenly distributed in the coil of wire. Even if the magnet were to be centered with the magnet, the space between the north and south poles of the magnet would experience a lower field strength. And, in the case of a coiled magnet, the field strength could vary inside of the poles; therefore, converting some voltage into heat and motion. I feel that you should retest this on a bigger scale; so that, you could observe if there is any transformation, or uneven distribution of energy.

  3. isn't that a pointless exercise? It what situation would that matter??? I wish they would get into proper scientific experiments and stop faffing around with idiotic theories like this one!!!

  4. some late thoughts. as others have observed, the statement acknowledges the (universal) affects of induced current; a la faraday. there is a flaw in this testing apparatus/approach. what produces a VARYING magnetic field. in the case of a solenoid, the field varies ONLY until saturation occurs. at that point, variation in the mag-field ceases. (you can choose the pulse width/strength.) googletranslate

  5. I am not a physicist, (I am a radio engineer). The “probing” across the resistors with the test leads orientated to cancel induced voltages makes sense to my instincts.

  6. Any instrument can be wrong or inaccurate, those scopes could easily be slightly out of tune. Not to mention that some magnetic fields create more current in one direction than the other, so the probes will show difference.

    >Dr. Lewin's theory only holds up when the sense lines are also curved
    I see I see, yes. So what I'm hearing is that it only works when he uses it as the component he leaves out of his diagram

    Proper shielding and proper probing, I think you're right Mr. Mehdi

  7. The problem is mostly one of semantics. Dr. Lewin isn't wrong, and neither is Mehdi (except for his speculation as to how to "correctly" measure the voltage at 11:55). It comes down to how you define "voltage", and there are different ways of doing this.

    If your definition of voltage is the quantity such that the electric field is the negative gradient of the voltage, then KVL does not hold in general in conditions of time varying magnetic fields. The sum of voltage drops along a loop is equal to the negative rate of change of the magnetic flux through that loop (Faraday's Law), and Dr. Lewin is correct. There are other problems with this definition: the problem highlighted in this experiment applies equally well to all inductors. According to this definition, a perfect inductor (with no internal series resistance) will always have zero voltage across it, regardless of its state in a circuit. In practice, we can restore KVL in circuits containing inductors by thinking of inductors as hypothetical components with the usual I-V relation: V = L*dI/dt.

    We can define voltage in another way, which is more in line with Mehdi's way of thinking. It can be defined as the scalar (or electric) potential of electrodynamics (see for the definition, involving the magnetic vector potential). The scalar potential is always well-defined and unique (up to an additive constant), including in the presence of time-varying fields, and agrees with the previous definition when there are no time-varying magnetic fields. With this definition, Faraday's Law demands that the sum of voltage drops in a loop adds to zero, which is just KVL. The usual I-V relation of inductors is also in agreement with this definition. There are disadvantages to this definition though: it is not always obvious to tell what the scalar potential might be at a given point of a circuit. Mehdi does a good job of explaining what's happening to the scalar potential in this particular circuit, at 10:47 onward. This illustrates that there are "voltage drops" along sections of the wires connecting the resistors, which is not necessarily intuitive. A second (and related) problem is how to measure the scalar potential, and I don't know off-hand if there is a straightforward way of doing this for a given circuit. Mehdi's suggested way of probing at 11:55 is in no way special, and does not guarantee that there will not be scalar potential drops in wires connecting the two points to the voltmeter or oscilloscope.

  8. I rather think that Dr. Lewin as Dutch guy just is annoyed by the german Kirchhoff and prefers the british Faraday.

  9. as you said it all depend on probing, I can measure lets say switch mode power supply for voltage ripple and have different results based on how I usedheld my scope probes, so completely agree with Mehdi on this, professor is probing it not correctly!

  10. Some Krich law has been debunked

  11. The comments about a certain video host not receiving a shock proves said host's theory. The sum is zero, obviously!

  12. i feel that I am lucky because on one of the videos of walter lewin I commented and he replied back to me

  13. No idea what you're talking about, but pretty familiar with the old chestnut of established 'masters' thinking their sh** don't stink. If you make a mistake, admit you're wrong and move on or you're no longer contributing (ps I was sad not to see any electrocutions and minimal swearing in this vid 😉 )

  14. I was watching the test wires make a similar loop to the resistive loop being measured, and wonder why the drawing wasnt showing the resistor pair loop, overlayed with the 100M ohm resistive loop of the meter. The coil was inducing both loops. Right there I just instinctively thought "the measurements are invalid" What if the meter probe wires were emf shielded?

  15. An year ago I understood nothing, now till 3:54. Now let's see how much time it would take me to understand the rest of the video.

  16. Bad probing??
    Regarding the so-called issue of "bad probing", most people would be unaware that the company Maxim Integrated produced a device which makes use of the properties exemplified in the two distinct meter readings of the Lewin demonstration. This presumably should put the argument to rest, otherwise why would a highly technically competent company like Maxim go to the cost of developing a device which employs a flawed methodology of "bad probing"?
    Details can be found at the Maxim website as an application note AN2238 "Position sensor exploits Faraday's Law".
    It is also worth checking another application note from Maxim: AN3651 "Circuit Analysis in the Presence of Time-Varying Magnetic Fields"

  17. I watched this video before one year and did not understand a thing but now that I am in love with electricity I understand and support your claim

  18. Electromagnetic Potential is a 4-vector-field-up-to-gauge-transformation. Specify a Reference Frame and a Gauge Condition, otherwise we are not communicating.

  19. Walter disconnected comments and in some classical mechanics video, old textbooks disagrees with his opinion.

  20. I think I speak for the audience when I say that your hypotheses are more lucid when you inserpose your chest hair and fingernails into the circuits at the higher voltages … 😁

  21. Interesting stuff. I think it comes down to whether you can define all the magnetic fields in a closed loop, and where they are, or if there is at least one source that can't be defined (location, flux density, rate of change in the field, etc) but is known to exist somewhere in the loop.

    If you KNOW for sure there is a changing field in the loop but it can't be defined in any accurate or practical way, then yea, things get complicated and KVL won't work because things that are happening are not shown when doing the electrical analysis. But if you can and do define it, KVL works.

    Nice job with the probes. I learned something 🙂

  22. Great video, and the best part for me was realizing you "forshadowed" the answer right at the begging when you explained why you twisted the wires of the scope….whether you meant to or not haha

  23. This is a just terminological discuss. You take in account the inducted voltages during your calculations. But Dr. Lewin says that Kirchhoff Law doesn't discuss about inducted voltages. The critical point is that "is it needed to take into account the the inducted voltages (in terms of Kirchhoff Law) while talking about nonconservative situations?".

  24. 12:32 I absolutely agree. I had the same thought, at the beginning of this video: That the changing magnetic field must be inducing a voltage in the wire, that must be included in the Kirchoff equation. It's not just two resistors, and a current–the induced voltage causing that current needs to be included in the analysis.

    It's funny, because I was just, earlier today, telling my wife about arguments I had with one of my college physics teachers. So, right-on Mehdi, fight the power!

  25. You convinced me.
    The old man is definitely senile.
    I now understand kvl. You explained kvl better than my professors in college.

  26. When you reposition probing wires and the result changes it's obvious that those wires are important part of circuit.
    No engineering education needed, just common sense.

    I thought you make the wires perpendicular to the loop to remove the influence of the coil (would it work?)

  27. KVL only holds under the condition that the elements in the circuit model obeys lumped matter discipline. By extension of these limitations, Dr. Lewin stands correct – at least in saying Kirchoff's law has limited applicability.

    It was silly of Dr. Lewin to disprove something by violating its underlying presuppositions – and silly of you to prove KVL by capturing the flux around the loop in real time to show for inductive losses at the time of dc on-off. In neither case is KVL actually disproved, or proved conclusively as both experiments don't fall within its scope of application. The Wiki article on Kirchoff's laws states explicitly that it is derived for a subset of low-frequency applications including dc (where inductive losses are next to none) and Maxwell's would be the way to go for all other applications.

  28. The response on this video by mr lewin could have been milder. I posted this comment on his response video as well.. i'm posting the same here. it appears that what professor lewin is saying is that you cannot account for the differences in voltage measurement using the simple and orignal form of the kirchoff law statement.. the kirchoff law does not contain the dpsi/dt term and hence cannot account for changing magnetic field.. for a second if we stop thinking about voltmeters and think about an ammeter in the circuit, we will realise that kirchoff law applied directly to the circuit by a third party observer who only knows the resistances and the current in the circuit will fail.. the third party observer will say there are non net zero voltages in the circuit for some unexplained reason.. however for someone who knows there is a changing magnetic field like electroboom, he will try to account for the voltage by means of the transformer formed in the circuit (which is correc also) … the only difference is that electroboom is aware of the changing magnetic field and therefore is forced to put a transformer in the line to keep everything aligned with the known laws of physics.. however in doing so he has added a component in the circuit which is dependent on the dpsi/dt term which is not part of the kirchoff law in its original form.

  29. Professor lost this match, I suppose.
    I looked throw his wiki page and a "list" of scientific discoveries.
    There is none. None useful, tangible thing. The only idea is a rotating neutron star. He is a classic "bla-bla" relativistic scientist.
    Neutron stars are theoretical objects we do not know whether they exist in the first place. The neutron matter is a theoretical imaginable substance which was "sucked from finger" to hold the star together while otherwise it will be disrupted by the centrifugal force of rotating superspeed.

  30. I’m glad you did a video on this. I watched the MIT video years ago and taught how could someone so smart be so dumb. It is obvious that the voltage difference is due to the placement of the leads. Keep up the good work.

  31. I think you nailed it. It would be cool if there were some kind of miniature surface mount circuits that you could insert around the loop that would transmit the value of the current instead of trying to probe it with leads. Instead of measuring the voltage what would happen if you measured the current around the loop instead with a tiny torrid with a winding on the torrid going to your scope?

  32. When I did my electronics study, we were simply told that KVL and Ohms law only hold at DC, all bets are off when you introduce rates of change.

  33. Hadn't seen both sides of this before today, but my conclusion was the same as yours the second I saw how he makes the conclusion, Kirchhoffs Law should hold, in any case, I'm not as educated as Lewin, but I have a general understanding of advanced physics.

  34. Interesting video; I also come down on your side. And not because as a mathematician, non-conservative fields intimidate me. Here is my summary I just posted to the professor; secretly hoping for the link-spam-treatment.

    Yes, given a non-conservative field with a curl, a scalar potential is path dependant and hence not defined, generally. But for the sake of analyzing a given concrete circuit realisation, the fact that one may consider alternative circuits too with different induced voltages is not too relevant.

    So for a given fixed circuit, the question of the KVL is really a definitional one. If we count all induced currents as voltage differences over their respective components, (as is quite customary in circuit analysis), then KVL holds. If you put those EMFs due to changing fields on the right hand side, and don't count them as a voltage on the component, as maxwell equation would have it, then it does not.

    But the bottom line is that one can do circuit analysis with full faith in the KVL law, as long as you stick to your definitions of how to compute and account for induced EMF's. The supposed experimental contrary evidence to that is indeed correctly refuted by electroboom; they are simply an example of exactly such inconsistent accounting; ignoring the EMF in the probe wires.

  35. Man now that I'm looking back at this video, I can see why Walter Lewins got mad. ElectroBOOM said his error was due to bad probing. For one of the world's best professors of physics to hear that from an engineer, he must have felt pretty insulted.

  36. Kirchoffs laws have held up fairly well for over a century. ! They have been the basis of theoretical physics and practical electronics in modern times. The basic principle that says plus one added to minus one equals zero is indisputable. If one were to pick a sine wave and add its plus and minus values together you get zero . However if you choose two points independent of time and use those figures to disprove a theory then you are wrong . The sum of voltages in any circuit must add up to zero otherwise the law of conservation of energy goes out the window !

  37. Mmmm i find this very interesting… i'll consider your point of view as possible, i'd like to attend a Dr. Lewin class considering this information, that would be great!

  38. I'm a rookie but KVL is true, but that is in an ideal circuit. We have a lot of outside influences. I will side that even ones body can influence the circuit, but that can also be said with outside forces. But this is completely negligible to impact in any form of way.
    My opinion, but thanks for another great video!

  39. This video illustrates why I subscribe to your channel. While the majority of your videos have an important entertainment value, they're based on scientific principles. I appreciate the level of critical thinking you are able to apply to the many scientific laws of electricity. Thank you for the work you put into your videos.

  40. Your logic is spot on. Unfortunately, the professor has made an error. Heck, even Einstein, Hawking and every other scientist has made errors.
    However, in this instance, it could actually be blamed on his advanced years.
    Well, that and his fashion sense. Sheesh, that shirt probably has a wattage rating!
    Anyway, great video.
    Thanks for sharing!

  41. Thumbs up!
    If you have a master's in engineering, i have two dogs.
    KVL holds: the professor missed the fact that the wires are non-zero length. Given Faraday's law, they should be modeled as a voltage source.
    If the wires are infinitesimally short, voltages measured WILL be the same.
    With all due respect, physicists know physics, not engineering!

  42. yup just watched the reply to the replies … interesting little oversight … I knew something was off … but wasnt sure what or why … I knew it had something to do with the magnetic field but not in what part or why …

  43. for example, do the same experiments not in the middle of the ring but on other points. kirchhoff laws are not fundamental, the maxwell equations plus conservation of charge are

  44. Thanks very much. I am glad to have seen your demonstration, and becoming a little better illustrated in the process.
    Despite the great admiration fo Walter Lewin i have, i understand that you are completely right. So, very much thanks to you again No awards nor prestige can go over facts

  45. One of my subscribers just turned me onto your videos. Absolutely magnificent stuff your brilliant! Going through most of your videos now it's going to take me awhile, but I'm having a blast. Thanks for sharing

  46. so the miscalculation was from the sense line. or the measuring apparatus. certainly elementary.
    this reminds me of the double slit experiment.
    great episode, thumbs up in hopes he views your video and replies to you.

  47. I think the reason you and so many people like you have this "religious" belief goes back to making robots out of humans. if you're a scientist you don't care about the results you care about how you get there so guess what; using a meaningless eq to get the "right" answer is unreasonable even for an engineer. so use faraday's law you dumbass

  48. Rather than challenge Prof Lewin, review the submitted paper on which Prof Lewin's argument is based on, and repeat the experiment, compare with your own findings, and if it still disagrees, then submit your contradicting paper. This is the principal of the scientific method. If you're right, you could be famous! 🤘

  49. This is why we have theoretical, ideal, and practical models. Kirchhoff's law can never be tested(perfectly) but it is theoretically correct.

  50. I only have a Bachelor’s degree in Electrical Engineering Technology but I really question the sanity of someone that gets 2 different voltages at 1 node. That always means you’re measuring wrong.

  51. This video is a perfect example of the difference between an Engineer and an Academic. An Academic would love to disprove something like Conservation of Energy, an Engineer uses it every day and knows if Kirkoff’s law doesn’t hold it’s because you’re making a mistake.

  52. The prof's video is just disappointing. Mehdi made a 13 minute video, tried hard to explain his thoughts and did a bunch of experiments. The prof just refers to few of his previous videos. In the comments then he's behaving even more inappropriate, acting like a incorrigible and despicable mastermind, copy'n'pasting the same comment again and again. He as well comments things like: "All relevant videos are on my youtube channel. You can lead a horse to water, but you can't make him drink. Most of Electroboom's followers don't want to drink. It's their choice to believe in wrong Physics and that's fine with me. I also have no problems with people who believe that the Earth is Flat." The prof is offending all of Mehdi's viewers, just because he doesn't want to say why Mehdi's conclusion is wrong and constantly referring to some of his previous videos. A good prof would try even harder to explain when a student came up with something like that, but he just offends Mehdi saying it would be 1st grade college content, and that it's worriesome to not know such things having a master in EE's. Prof Lewin either doesn't want to accept he made a mistake, or he's just an old, stunted and disrespectful prof, who's ego has grown up to the moon. The last one is more likely.

  53. Very nice analysis, thank you. I was kind of wondering if the mysterious measurements were due to bad probing, and you proved it. The universe will not collapse after all!

  54. 4:48 "I have a coil or solenoid"… Me: This is going to explode.
    4:57 "The resistor limit the current to 10-12 Amps"… Me: This is going to explode.
    5:30 "Now I'll measure across these two points…" Me: This time for sure.

Leave a Reply

Your email address will not be published. Required fields are marked *