Hello team RECTIFIER! Make sure to watch the next video on the topic: kzread.info/dash/bejne/g22A17h7ltrcqqQ.html

@ozule1782

5 жыл бұрын

ElectroBOOM ok

@riveralley

5 жыл бұрын

Stop looking at the camera it feels like your looking deep into my soul.

@TheDonkeyofdoom475

5 жыл бұрын

I agree

@NotArielPierson

5 жыл бұрын

I like how you challenge the norm, fight for the truth even if you have to oppose the majority! I hope you're indeed correct and get to have your own claim on humanity's understanding of all things electric!

@patrickwatkins7572

5 жыл бұрын

HMM... there is no common earth, thus its unfair. - i bet your anomaly disappears. if you common eath the scope, too a fixed point on the input induction bolt coil.. for both tests.

You can tell he's serious because he doesn't shock himself in this video.

@imyourpcguy8477

5 жыл бұрын

haha! +1

@angelomartino4667

5 жыл бұрын

Well, I didn't understand anything but the fact that he still shocked some scientists out there

@davemwangi05

5 жыл бұрын

@@angelomartino4667 hehehe.

@bravojr

5 жыл бұрын

Also the altitude of his Eyebrow~s~

@Originalimoc

5 жыл бұрын

lol

"I couldn't be happier to be wrong and learn something new." -an important moral fiber rare these days.

@rot_studios

5 жыл бұрын

So true. It's something that bothers me in almost every discussion I (try) to have with people, the rare exceptions excluded of course. Yet it's so great to be wrong! Because now you now know better and have become a better person for it. What's not to love? :D

@Solua86

5 жыл бұрын

Yep

@dimitriss.7954

5 жыл бұрын

I literally read this the same time Mehdi said it Are you Illuminati?

@konorkoler

5 жыл бұрын

@@dimitriss.7954 I am working on it my friend.

@CODMarioWarfare

5 жыл бұрын

"These days" Nah that's a universal human bias

Bad probing is almost always the number one source of error in electronics experiments. Kudos Mehdi

@Pharos963

Жыл бұрын

My thoughts exactly! Thanks for saving me from having to comment this.

@londen3547

7 ай бұрын

@@MikeDonaldson-eh2ru I've watched several of Lewin videos, the guy knows his stuff but often doesn't bother to explain....must be an MIT thing, gifted students expected to figure it out on their own.

Can i just say that watching both this and your follow up video, i think the best lesson to be learned here is how to handle a disagreement like an adult. You found someone who had reached a conclusion that you disagreed with, and were still respectful of their findings and knowledge, while showing the reasoning that lead you to disagree. If more people could handle their disputes like this the world would be a happier place. Best wishes to you.

@SerialWaffleStomper

4 жыл бұрын

Couldn't agree more

@pearz420

2 жыл бұрын

He did everything he could to be tactful and respectful and still got gruff. You can really tell no one has disagreed with Lewin in at least 30 years. He handled it so poorly.

@d4slaimless

6 ай бұрын

@@pearz420 I kind of can see where prof. coming from. When people bother you with stupid questions and provide their demonstrations that doesn't make sense then after a while you just decide to stop going into any discussions. Maybe he had enough as educator. Of course he could have handled it better. I mean ElectroBoom certainly makes not only entertaining but also educational videos. And it would certainly benefit both of them to make a constructive argument.

Very well done and diplomatic ;)

@Token_Nerd

5 жыл бұрын

And the civil engineer shows up trying to play around with the electricals.

@_aullik

5 жыл бұрын

@@Token_Nerd You shouldn't anger a civil engineer. They usually design civil structures in a way that they can hide bodies inside.

@Token_Nerd

5 жыл бұрын

@@_aullik As a Civil Engineer, no comment >;)

@WG55

5 жыл бұрын

And civil engineers are experts in civility!

@Markle2k

5 жыл бұрын

@@89rafa Very subtle pun.

I am surprised that Dr. Lewin did not consider the mutual coupling of the coils with each other in his experiments. In his test moving the probing wires around should change his results. I could not find anything wrong with your analysis. Dr. Lewin seems to verify his hypothesis through the demonstrated experiment which appears to be flawed in how it is setup and yields an incorrect result. First step would be to correct the setup before we even discuss the issue at hand.

@TheAmmoniacal

5 жыл бұрын

God has spoken.

@jaoswald

5 жыл бұрын

I think this is more an EE/Physics communication barrier. The physics view is that the EMF is not strictly a property of the circuit (and which points you choose), but of the full path enclosed by the probe wires and whichever part of the circuit forms the rest of the loop. Time-varying magnetic flux changes the situation from being a conservative potential (safely path-independent) to one where the loop integral is path-dependent. When @ElectroBOOM talks about "bad probing" or "good probing" it essentially is defined as "arranging your probes to avoid encountering the effects of flux in the path segment outside the circuit. I.e., suppressing exactly the difference Levin is talking about. When he introduces a transformer into the model, it is incorporating the probe wires into the circuit as the secondary. The controversy is about how one classifies these issues of measuring the voltage and whether they are included in the meaning of KVL or not.

@laharl2k

5 жыл бұрын

he's reading a 1 turn coild with some wires that act exactly like a 1/2 turn antiparallel coil. Of course it's gonna negate half the reading, and you dont even need to flip it. Moving the wires most change the reading because he is litteraly adding 1 and substracting 0.5

@ricardonunes6724

5 жыл бұрын

I also think this is an EE/Physics communication barrier. Faraday's Law is very clear. The voltage in a closed loop is equal to the time derivative of the magnetic flux. If there is a time varying magnetic flux present, the voltage in a closed loop is not zero and Kirchhoff's Law doesn't hold.

@ABaumstumpf

5 жыл бұрын

@@ricardonunes6724 "If there is a time varying magnetic flux present, the voltage in a closed loop is not zero and Kirchhoff's Law doesn't hold." no, that is simply false. It holds true for dynamic systems just as well.

Teacher: The test isn't complicated The test:

@PafiTheOne

4 жыл бұрын

Teacher: predicts result, Teacher: conducts experiment Measurement: agrees with predictions Former engineer: Nooooooo! You can't hit me!

Your regular, humour-filled videos with shocking situations that make you want to go Ohm, are nice and I love them, but this video was really refreshing. Seeing you explain a confusing topic and simplifying it down so those of us, not too familiar with electronics yet can understand...dude, I need more of this. I think that is a legitimate sign of intelligence.

"my mom thinks I'm mostly ok." 😂 r e l a t a b l e .

@peterwilson69

5 жыл бұрын

lol - yeah, I was glad to hear that too.

@12Deathcon

5 жыл бұрын

So I'm not the only one who has received that statement before 😂😂😂

@plushifoxed

5 жыл бұрын

the rectifierrr

@lukemontgomery9683

5 жыл бұрын

Yeah my mom thinks I’m ok kinda.

@heanstone1327

5 жыл бұрын

Mostly lmao

Interesting to see you challenging Dr Lewin. Science drama is so much better than typical KZread drama. And this is science drama _on_ KZread! A new paradigm!

@berni8k

5 жыл бұрын

Id enjoy drama a lot more if all of it was like this!

If you don't understand anything, it's fine. He is not explaining it you, he is explaining it to Walter Lewin XD

@maheshwarannarayanan

3 жыл бұрын

This is the comment I was longing to hear....though I could grasp it up , still I didn't feel like I completely got everything he said

@8kigana

3 жыл бұрын

hahahahaha

@karoly365

3 жыл бұрын

You are just the alibi for the KZread revenue

@anirudh2000

2 жыл бұрын

@@karoly365 truth hurts man, but truth is truth

@yashrathi6862

2 жыл бұрын

It's high school physics

What I got (reinforced) from this is that even the wire is a circuit component. Since the sense wire folds back on itself and follows about the same path back around, it induces nearly equal but opposite current from the wire that it's adjacent to, cancelling itself out. So you only read the effects of current through the opposite resistor. At least, that's what appears to be happening. He touched on that near the end when he drew in the hidden transformer.

"My mom thinks I'm mostly ok." It's ok Mehdi. We're all in that boat together. Love you man. Keep up the great work!

@theterribleanimator1793

5 жыл бұрын

My mom doesnt know what to do with me anymore.

@davecrupel2817

4 жыл бұрын

My mom disowned me :c Jk shes the best mom ever.

@meenamathew8248

3 жыл бұрын

that ws sad

@mohawksniper79

3 жыл бұрын

My mom does not have the same feeling about me Infact it's the complete opposite 😁

And this is why science is based not on authority, but on peer review.

@youtubasoarus

5 жыл бұрын

Or facts born out of evidence? You could argue that a bunch of professors could claim something erroneous and it would still be peer review (collective delusion or even collective error in methodology). But they cannot dispute facts.

@J624

5 жыл бұрын

@@youtubasoarus Be careful saying that. Anti-vaxxers and flat-earthers dispute facts all the time.

@RealCadde

5 жыл бұрын

Consistently reproducible results i'd say. "What if i test your theory this way" which is exactly what mehdi is doing and coming up with a different result. Hence, theory needs adjusting.

@fordman7479

5 жыл бұрын

But then it isn't really is it? Never really has been, there's probably more politics in the scientific world than in the White House. Science is dead like in around the world in 80 days, it's all about theory and what theory is popular.

@MrDoboz

5 жыл бұрын

@@fordman7479 110% agree

I come to this video from time to time hoping I can understand all the concepts explained here a lot better. Out of all Mehdi's videos, this one does even more hard science than Mehdi usually does. That being said, I have learned quite a bit from this great dude, and I do appreciate the fact that he shocks himself a lot just for the laughs and to enhance the learning experience.

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

I am really glad you did this video, not just cause I agree with you. It can be scary to challenge the findings of someone you respect but I think he would respect that challenge because we'll science.

@GigsVT

5 жыл бұрын

Unfortunately dogma is big in science as well. Look at the oil drop fiasco.

@andrei-lucianserb1771

5 жыл бұрын

Can anyone show me where the professor says that Kirchhoff should be changed because it is not correct, and where exactly is the experiment that he did and that he says shows this. Why are people pretending that the professor is attacking Kirchhoff. It is clear that what he is doing is showing his students that when you make an experiment where you don't take into considerations the very well known limitations of Kirchhoff, you will get the wrong results. Not probing in such a way as to make Kirchhoff work was the whole point of the experiment. It was to show that not adjusting for the effects caused by the limitations will produce bad results. I am absolutely dumfounded that people legitimately thing that the professor doesn't know how to probe a circuit, instead of thinking that he is doing so intentionally in order to show his students the dangers of not fully understanding Kirchhoff laws and their limitations.

Oh, I worked in that field - years ago. The KVL is derived from "E = -grad( phi )" and the corresponding integration theorem. If there is an time varying magnetic field, the true electric field is "E = - grad(phi) - (dA/dt)" . I.e. the KVL holds in the electro-quasistatic approximation assumption, that dA/dt is approximately 0. The KVL is false otherwise.

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.

@TheKb117

4 жыл бұрын

not today my friend, not today.... he had to be serious when refuting against a distinguished professor

@Magneticitist

4 жыл бұрын

Whenever you see him use a capacitor and plug something into a power supply it's a done deal

@samircaldasaiala2959

4 жыл бұрын

That is true i though the same way 😂! I am not used to this kind of video from him !

@johnrubensaragi4125

4 жыл бұрын

Don't worry, the pulse is short.

You were totally respectful and very educational with this video. The net result is more people learning about electronics, so I think this is a wonderful video.

@maximmarchal9991

5 жыл бұрын

Agree! I've studied EE and I've come across this particular subject. I just assumed the lecturer was right at the time, but Electroboom got my gears grinding again, which is probably his goal.

Hi, I'm a theoretical physicist. I don't think Prof. Lewin was completely wrong, but I don't think your reasoning is wrong either. I agree with your calculations, but I think you are not applying Kirchhoff's law as is usually understood from the physicist's point of view. One may argue that Prof. Lewin is also wrong for the same matter when he says that Kirchhoff's law is sometimes wrong. It is never wrong: it's just that it does not apply on certain systems. In the end the problem, as I perceive it, is a semantic and not a physics one. What I am certain, though, is that Lewin proved himself to act rude and arrogant in that comment box. Your objection was completely legit and he had no right to call you an uneducated.

@furkancalskan9359

5 жыл бұрын

As a mechanical engineer and amateur electrician, I was here for type a comment like this one literally. I totally agree with you. Dr. Lewin may right about KVL is not applicable on some circuits but that doesn't make the law "wrong" because it is not a theory. It is a "Law". Even if Mehdi is not right at all, it is not ethical to call him "uneducated".

@tealiedie

5 жыл бұрын

As an asshole. you were all wrong.

@furkancalskan9359

5 жыл бұрын

@@tealiedie So Mr. Asshole. What is the truth? I am looking forward to.

@furkancalskan9359

5 жыл бұрын

@sudan suwal Mr. Suwal, please could you explain which argument that I posted above wrong? I am really wondering it. Actually not intend to kidding. I just want to know if I misunderstood something in electrical circuits. I'll be wait for your response. Good day.

@edyartzi

5 жыл бұрын

You are completely right. The professor is making the mistake that measurement of an experiment has to be the same regardless of the probes. The fact that you get different results measuring the same thing means that something is wrong with the experiment, automatically any conclusion is wrong. Testing Kirchhoff's law in the professor ‘s experiment is the first mistake. The conclusion is a ridiculous mistake. I’m a professor so I can say what ever I want that is no mistake. That is a fact.

From another Electrical Engineer- you got my vote👍

@davemwangi05

3 жыл бұрын

I've got an awesome relatively easy invention in electronics. would you be interested in a collab for improving the design, etc? maybe even patenting?

@gustavotasquer7389

2 жыл бұрын

my vote too

@hot-blizzard-lol7558

2 жыл бұрын

As ways Mehdi>pedophiles

Came across your channel by accident, it took a couple of videos but ya grew on me lol. Love the honesty, if ya don't know or not sure you say so. Great job dude

This and the follow-up part 2 video are my two very favorite videos of yours! Your passion is for the science itself...finding the truth...This is the same passion, Faraday, Maxwell, Feynman, and the other greats all shared...You're in good company! Thank you for this series and for the inks to the counter-arguments by Lewin...

Great scientists admit when they are wrong and let everybody learn from their mistakes; those other scientists get their ego punctured.

@juststeve5542

5 жыл бұрын

Indeed. Science is about the continually challenging and testing ideas and theories. Peer review is a cornerstone. If you refuse to permit your claims to be challenged then you're a religion!

@khaoscero

5 жыл бұрын

It doesnt necessarily have to be ego, but it can be very deeply rooted ways of understanding the principle. Especially for someone who does nothing but this for decades, you cant just step back and view it anew.

@nialltracey2599

5 жыл бұрын

Nope. Walter Lewin is a great scientist, but great scientists are still human beings and still get caught up on personal bugbears that don't hold up to scrutiny.

bro curl(E)=-B_t (where B_t is partial derivative of B with respect to t) is a maxwell eq. it is always valid. while applying kvl u assume that E is grad of some scalar function, if a vector field is grad of a scalar func, then it must be curl free. however we know that curl(E)=-B_t, thus kvl is not always valid, which assume curl(E)=0.

I agree. I'm an OLD electronic tech/engineer and have seen this sort of thing come up as a problem in a industrial installation.

Howwwwlyy Shhieeeett!! When I heard "2 different Voltages across the same 2 points", I questioned my life and all circuits that I ever made ^^ Now that I saw the great explaination it all came together for me. But I do agree with you. It does make a lot on sense when you think about it.

@mdhz786

5 жыл бұрын

You're not alone.

would it be possible for you to start a lecture series about circuit analysis? i believe you are the best teacher i know. theory combined with actual applications/experimentations is the best way to learn. i haven't been bored in any of your videos. you're so good! more voltage times current to you sir!

@sarmadrafique4472

5 жыл бұрын

That would be great...

@GiaZera

5 жыл бұрын

Bring this to the top, people! We need more Electro101 videos!

@enchantedgames6589

5 жыл бұрын

My god..... How about you stop writing cheesy comments and go and force times distance.

@grimjogaming878

5 жыл бұрын

I'll support this ❤️

@katlegomokwena7524

5 жыл бұрын

Ramon Cristopher Calam this would be highly appreciated!!!!!

Very well described! I work with small signals from microphones and phono cartridges and your video explains extremely well what happens in low inductance and low resistance loops and induced currents. Well done!

This is a very good point, though several times before when I watched the video but didn't realize how important it is. The matter of this question is how to model the real physics system: we can model the magnetic field by inductances and transformers as electrical engineering, while physicists may look at PDEs and have less emphasis on lumped circuits. As for the probing, that's another vital lesson I have learnt, because I was lucky enough that I didn't burn the scope with ground circulation with two passive probe at a region of high di/dt, quite similar as here.

I was working on this same experiment for a Book. And I couldn't find a Simple way of explaining this. You did it in just 15 minutes which is awesome. This is very well done and quite diplomatic I must say.

@therealb888

5 жыл бұрын

Well he works in electronics & has an MS in it.

@sanketpawar4253

5 жыл бұрын

Do you really think that his explanation is right??

@RedTriangle53

5 жыл бұрын

Not to be rude, but maybe you should wait with your book until you know what you're writing about. Mehdi is completely wrong, and what he is proposing is in direct contradiction with maxwell's third law. Kirchoff's voltage law does not hold under varying magnetic fields and has never in history been thought to. As a matter of fact, if it did hold generally we could not have engines, generators or electromagnetic waves. If you believe in the existence of those things I suggest you take another look at the theory. What mehdi did was to 100% verify the effects and then without much of a reason just dismissed them as "probing errors". They were not probing errors, they were vital parts of the experiment. If only it was this easy to disprove electromagnetism. I bet he would "disprove" gravity by showing a falling ball and saying that if only the gravitation didn't cause a probing error it would just float there.

@ricebubble7805

5 жыл бұрын

I like how your comment says "very well done and diplomatic" almost exactly the same way that other guy's comment says, and he posted his comment a day before you... COMPLIMENT THIEF AHA

@bhimj9340

5 жыл бұрын

You're stupid

I like how respectful this video was towards one of the greatest minds in out current time. Its not bad to disagree with someone and politely explain why. This is a great science video with awesome explanation AND a great guide to social communication. Good for you EB!

@adityamohan1773

5 жыл бұрын

"Current time" !!!!

@jamesrindley6215

5 жыл бұрын

Smart guy yes, but one of the greatest minds of our time? Hmm. Hardly Stephen Hawking.

@88werwolfhun88

5 жыл бұрын

He is fuckin' smart, but far from the greatest minds.

@BizarrelyOdd

5 жыл бұрын

@@88werwolfhun88 that why I said "ONE OF the greatest minds". Otherwise I would have said THE greatest mind.

@hank993

5 жыл бұрын

If Lewin was so smart he wouldn't have been stripped of his emeritus professorship for sexually harassing students. Arguing about incomparable achievements is pointless. So is the fetishization of hands-on knowledge. Takes all sorts to make the world go round.

Kvl is a simplified form of Maxwell's equation obtained by lumped matter discipline in which we assumed dphi/dt = 0 I.e zero change in flux.

@technics6215

2 жыл бұрын

Electrical engineers compensate dphi/dt change by taking into account inductance/emf on equivalent schematic. dPhi/dt exists as voltage induced in the coil/wire. So electricans actually use... Maxwell equation with dphi/dt "hidden" as emf and everything works perfectly. So... they both wrong?

The first serious video in this channel 😂 A lot of love to Elctro Boooom

Always express you thaughts. Just because he wrote 15 science books doesn't mean he Is right, or that he Is smarter than you.

@yasyasmarangoz3577

5 жыл бұрын

Yes! And if it is a teacher it also doesn't matter

@AbhishekThakur-wl1pl

5 жыл бұрын

Matija Lekovic there is no point of saying who's smarter or right, his point of view differ to that of ElectroBOOM, that's all. No matter who's correct in the end as you learn everyday, either of them will learn the truth that will change their perceptive positively 👍.

@djapepedja

5 жыл бұрын

Tako je

@qzh00k

5 жыл бұрын

We are taught the periodic table of elements when it's a world of isotopes, neither idea or the science is wrong, but it's complicated.

@SpaceTimeBeing_

5 жыл бұрын

He is more Knowledgeable than Him, not smarter. Dr. Walter may be right, just like what Mehdi says.

You are correct I have experienced different measurement around the loop while performing some practical in my university even my professor were stoked to see that, but I realized later that I had bad probing. Well explained Keep the videos coming and always express it good to see what other people think.

@laharl2k

5 жыл бұрын

try probing shitty solder joints with a scope......you can get readings from 0 to 150V on a 5V circuit.....

@tarike5613

5 жыл бұрын

90% of people who liked this comment saw just some smart words and liked even without reading

@SpaceTimeBeing_

5 жыл бұрын

@@tarike5613 You sound like a stupid person who can't read. This person's comment is clear.

@Nematics_Lab

5 жыл бұрын

@@laharl2k yes

@ppsarrakis

5 жыл бұрын

@@SpaceTimeBeing_ i though the comment was pretty clear to,weird.

It's very brave of you to challenge someone like that. Keep it up

I don't want to take sides but Dr. Lewin's reasoning is sound. KVL as we know it from (lumped) circuit theory can be derived from Maxwell's equations as a particular instance. If the magnetic flux enclosed by the circuit (contour for the path integral) is negligible then the voltage produced by it is negligible and we get the known KVL for voltage. This is much better explained in Harrington's "Time harmonic elmag fileds" with a nice summary in Table 1-1.

May I suggest an alternative test for probing this circuit: Rather than having the probe wires in the same plane as the resistor loop, instead have the wires perpendicular to the plane of the loop (parallel to the changing magnetic field). Thus, no EMF would be introduced into them until they are sufficiently far away to make the effects negligible.

@davemwangi05

5 жыл бұрын

good girl

@ericcartmann

5 жыл бұрын

The alternative would be to use a real transformer and a AC supply...but clearly electrical engineers already know how transformers work.

@hashansumendra9230

5 жыл бұрын

also suggested that way, then prob won't affect by EMF

@galelazic478

5 жыл бұрын

I will try this later this week

@henchidos

5 жыл бұрын

The probes in walter lewin's experiment are not affected by the changing magnetic field already, because in the external loops there's not much going on, there you can safely apply kirchhoff's loop rule and that's why you can measure Vr1 and Vr2, because the same voltage is applied on the scope

This is a risk one encounters when delving outside of ones field of expertise. By ignoring the transformer created in his model, Lewin made a mistake that you clearly identify. Well done!

@jimmoriarty6964

5 жыл бұрын

Electrical Engineering is Applied Physics but I get your point

@berni8k

5 жыл бұрын

I came to the same conclusion before even watching this video: Spooky phantom transformer

@clusterfork

5 жыл бұрын

In true internet popcorn fashion, I'm trying to find out who's winning the argument here but I'm not reaching a quick answer. For example, I'm not certain Lewin ignores the transformer issue. See freepdfhosting.com/d5fc27ec92.pdf for the notes accompanying that lecture 16, check out Test 1 and Test 2.

@tommihommi1

5 жыл бұрын

@@jimmoriarty6964 but the dude's field of expertise is astronomy

@berni8k

5 жыл бұрын

@@clusterfork I think where this came from is that Dr. Lewin forgot to also include the transformer coupling to the wires that go to his oscilloscope. He sort of assumed that his oscilloscope is directly observing the voltage at those points. Or it could be that be knows what is wrong perfectly well and uses this as a way of finding the really bright students that figure out why this happens.

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.

@delanmorstik7619

2 жыл бұрын

Sadly, he missed the point of the proffessor. By definition KVL wall is not akways true, BUT you can fix that in practice. From scientific point of view the proffesor is rigth, from practical point of view it does not matter or almost

Hello sir, I’m not sure if I’ve understood your video but in my opinion what professor lewin is talking about is maxwell’s equations. One of maxwell’s equation says that in presence of changing magnetic fields, electric fields are no more conservative therefore the work you need to do to get from one point to another does depend on the path you take and potential difference is just the work you have to do divided by the charge you’re holding

I fully agree that the model is missing an inductor. The ability for a wire to be able to have current induced from a changing magnetic field needs to be modelled in the circuit as an inductance. Just like the lumped element model for transmission lines.

@berni8k

5 жыл бұрын

Exactly. Every wire with a length longer than zero has inductance, no matter how low its resistance is. Had these been ideal wires with 0 inductance would mean they have to also have a length of 0, this would make the diameter of this circle also 0 giving it no magnetic loop area and making it impossible for a magnetic field to induce a voltage in it, hence voltage on all nodes would also be 0V. This then matches up with the circuit of two resistors, there is no component capable of creating a voltage.

@Steve-du6ms

5 жыл бұрын

But where does the inductance go in the circuit? It is distributed everywhere in the loop, including in the resistors. Lumping it in a specific place is not an accurate representation of what's going on.

@johnbutts4725

5 жыл бұрын

@@Steve-du6ms Each resistor can be replaced by its resistance and a series inductor (ESL). Each real life wire can be replaced by a resistor and a series inductor (ESR & ESL). These elements are joined together with circuit diagram wires, which have no properties in real life.

@berni8k

5 жыл бұрын

@@@Steve-du6ms Every length of wire in the physical circuit would be replaced by a inductor in the schematic with a value equal to the amount of total loop inductance it contributes. Additionally all these inductors need to have a arrow drawn between them or a line along them to indicate they are coupled inductors that share the same magnetic field and each inductor should be given a dot at one end to indicate it going clockwise or counterclockwise to this field. When the probe connections are moved around to the left or to the right of the circuit this causes them to flip from going clockwise to counterclockwise, this flips the dot on the inductor, indicating it will create a voltage in the opposite direction hence why the probes going to the left or to the right side produce a different result on the oscilloscope. Once you include all these inductors the sum of voltages equations you should get a pretty close match to what the oscilloscope is showing. EDIT: Oh and you also need to include the inductor of the solenoid in the middle, it is also coupled to the common magnetic field and is connected to a voltage source. That is the voltage source that is powering this entire circuit.

@Steve-du6ms

5 жыл бұрын

@@berni8k The inductance needs to be added everywhere in the loop. This means that the voltage is induced everwhere in the loop, even within the physical resistors. So the model would include many, many mini-inductors, each with an induced voltage. The difficulty I have is that this cannot simply be lumped in a convenient place. So it is not obvious to me that the neat KVL circuit, with a source and lumped elements, emerges nicely from this situation.

I love this about a person of science. Challenge even the most established idea. Your humble nature shows, and is really appreciated. Good vid, as you demonstrate how the exact positioning of sensory wires makes a massive difference.

Amazing video, and bad youtube algorithm, even tho i been watching your videos for ages (and subscribed) this good quality video was never in my feed... found it by mistake, and i was like “this must be new upload- just to see it’s 2 years old”

Hi, I think that what you are missing is that is not always possible to consider an inductance to modem the changing magnetic field. For example you could consider a magnet moving near your circuit. From a mathematical point of view maxwell’s law says that the integral of E in a closed loop (which in electrostatic is the ddp) is zero if and only if the flux of the magnetic field is constant through the surface enclosed by the loop. Anyway very interesting video thanks!

I remember having a similar conversation with one of my instructors as well. He simply said, high tolerance applications, use Kirchhoff's Law. For low tolerance applications, use Faraday's Law. I doubt I would have caught this. This clears up a lot for me.

Maybe he was trying to challenge some unknown genius to step forward and call him out??

@ElectroBOOM

5 жыл бұрын

wish that was the case, but no. Watch my next video on this... hey did you call me a genius?!

@petertrast

5 жыл бұрын

@@ElectroBOOM Good catch! I saw the next video, too. You have inspired me, after binge watching all of your videos in one week, to finally start my new channel I have been thinking about for about a year (and to do some of your builds starting with the rolled capacitor). I may not agree with all of your politics, but I still think you are a genius :)

@arshuarshaq5043

3 жыл бұрын

@@ElectroBOOM CAN YOU PLEASE GIVE ME A MULTIMETER OR RØDE MICROPHONE PLEASE I BEG YOU !! PLEASE !!!

@Akarsh-

3 жыл бұрын

@@arshuarshaq5043 FO Beggar

@arshuarshaq5043

3 жыл бұрын

@@Akarsh- mind your words ! And he is a teacher to me !

YES! I saw the transformer, too. The sense lines are part of the circuit! (I was just an ME, not an EE, although I am a licensed ham for what that's worth.)

Two truly good and decent men struggling to teach the next generation!.. they should be proud of each other!.. Im proud of you ElectroBOOM!

Uh, if you get different readings, dependent an moving your scope/sense wires around, that might be the hint, that your sense wires and scope position are not just sensing wires, but part of the circuit you created.

@raphaelcardoso7927

3 жыл бұрын

Exactly. Needs a bigger model

@yuxuanhuang3523

2 жыл бұрын

yep， as long as there is an alternating magnetic field through those wires. there is going to be an issue. Try with shielded wires and that will work

@bleblo13

2 жыл бұрын

Yeah, I don't get how Walter Lewin didn't see this. It's something you learn really early on in physics, and something that definitely shouldn't make you think that something like Kirchhoffs Law is broken.

@biskwit2416

2 жыл бұрын

Yip, pretty fundamental from an engineering prospective. Change the probing arrangement, get a different result, then you know for certain that your probing stinks. Don't understand how Walter considered the probe wire as miraculously independent of the main loop and that running it close to the main loop was all that was required to prevent pick up. As an engineer, even the small loop between ground and tip of the probe can give you all sorts of nefarious results, never mind a 2 X 2 inch wire tied to a loop, forming another loop with the other half of the main one!!!!! The problem Walter has is that the integral of E.dl gives the INDUCED EMF. Walter is arguing that this is the ONLY EMF present. Nope and nope. This is akin to a free energy device and we know how Mehdi loves those!!! His simplified circuit and it's readings should be the final QED on the subject.

@biskwit2416

2 жыл бұрын

@@bleblo13 I love watching Walter and I'm going through 8.02, but just watched his lecture on ohm's law, which, interestingly, he gave the same treatment as KVL. His argument was because a light bulbs resistance changes with time, because of temperature, then it's not much of a law.????? I think he's got a bone with lumped model stuff, hence this and his KVL statement, even though KVL is based on the conservation of energy!

New to the channel (probably one of the best KZread channels yet). Love the video! and as an EE student, this totally makes sense, and I couldn't agree more. Keep them coming!

I am a law student who desperately wanted to study physics. I've searched for law stuffs, and KZread suggested me this. Thanks to KZread for realising my heartaches.

@asamanthinketh5944

3 жыл бұрын

Ouch, love of physics is really strong

@chrisallen9509

8 ай бұрын

So did you quit law to study physics?

11:00 KVL states that, i*R1+i*R2=0 (i !=0) => R1=-R2, given that a resistor is a "passive lumped element" and this equation couses a "passive element rule violation" since one of the resistances is below zero. So in that case KVL does not hold and the induced voltage should be calculated by the "integral E dl" which means that there exist electric field change (voltage drop) through the loop wire which has 0 resistance we assume generally and that is a contradiction.

@trevorkearney3088

3 жыл бұрын

Good points. Presumably you've watched ElectroBOOM's follow-up video in which he persists with this line of reasoning with respect to a lumped parameter model of the Lewin experiment. It's amazing what mental gymnastics people propose to rescue Kirchhoff's loop rule. For instance they would rather abandon Ohm's Law instead. Any reputable physics text notes that Ohm's Law applies in the quasistatic situation and we must therefore explain the Lewin experiment as the effect of both solenoidal and irrotational (electrostatic) electric fields acting along the secondary loop path. ElectroBOOM's explanation is one proposed by many. Unfortunately it is fundamentally flawed and amounts to a misdirection which, if taken as true, will lead prospective students into the same world of confusion originally suffered by Robert Romer.

I had been wondering about Dr. Lewin´s experiment since the first time I saw it. I watched it several times and had come to a similar conclusion. Since this is an air core transformer, any nearby wire is part of that transformer. Magnetic fields can have very complicated effects. Basically I´m glad you adressed this.

@noamgraham9006

5 жыл бұрын

Kirchhoff's law holds only in cases the circuit size is much smaller than the wave length that passes through the circuit from the source. This is called a Quasistatic approximation, wiki link below. The simplest example is an antenna: An antenna broadcasts an electromagnetic field to the environment by a changing current that runs inside it. If Kirchhoff's law was true, there would be no current running through the antenna (it is cut off by KCL KVL laws). en.wikipedia.org/wiki/Quasistatic_approximation

@BrosBrothersLP

5 жыл бұрын

@@noamgraham9006 no that is not true at least not fully. Also there is also the possibility of "short" antennas that are smaller than a quarter or half waverlength. but that is not what lewin is trying to show. here he is not working in HF areas

"My mom thinks I'm mostly OK" Words to live by brother.

For those of you who think Lewin is wrong, I suggest you apply Faraday's law in empty space. A changing magnetic field will induce an electric field even in empty space and not just in wires. This electric field is non conservative. Do you still think the potential difference between any two points in space is uniquely determined?

@johnflux1

2 жыл бұрын

Talking about potential difference in an electric field is not the same thing as voltage. If you placed a test charge at one of those points, would it actually move to that second point? If no, then that's not voltage. If yes, then you have the exact path that that test point moved, so yes, the voltage would be uniquely determined since you have the path.

Kirchhoff’ law is for static fields. Given this fact the argument is doomed as we already know we are in trouble. The voltage between 2 points does not make any physical sense if you have a time varying field. You can only measure voltage acting around a complete loop. So measurements depend on the path of the wires connecting the 2 points. Replacing the distributed induced e.m.f with a transformer is not valid. In reality there is an induced electric field acting on all the wire so replacing with a transformer does not model the physics correctly. Choosing a straight path between the points does not help anything. In short there are somethings which can not be modelled with a discrete circuit and this is one. To understand this properly you need to think in terms of fields. But as always very entertaining presentation.

I will watch this in front of my family, so they will think I'm smart

@dhirajbibekar5304

5 жыл бұрын

😂😂

@GarrettMoffitt

5 жыл бұрын

@@animeshpathak3921 Really? Come on there is no need for that, Apologize.

@animeshpathak3921

5 жыл бұрын

Ok.

@eshance-0944

5 жыл бұрын

😂😂i think that i am the only one

@bharatyadav8931

5 жыл бұрын

Clever man😂😂😂😂😂

Great discoveries are made by those who question the leaders of the field

@nullbeyondo

3 жыл бұрын

@LonerWolf Patriot That's the most ridiculous thing I've read today. Theories are never against reality. That kind of thinking bottlenecks our progress in science.

@alessandromorelli5866

3 жыл бұрын

@@nullbeyondo No theory describes reality perfectly, it is pretty obvious he talks about science's continuous ability to find better and more precise theories by challenging its previous ones all the time.

@alessandromorelli5866

3 жыл бұрын

@E it's not about being right or not, it's about testing, challenging and learning, that's the entire point of science. And most of the things ever tried don't work, but when they do, then we move forward, slowly but one step at a time. Any good teacher knows this.

@PonaHD

3 жыл бұрын

@E I think he is, tbh. Old people become so bonheaded that they refuse to listen to younger people. And for Dr.Lewin to call him uneducated when his arguments are valid is immoral and i don't like him for that reason... It's like trying to tell an old mechanic that what he is saying is wrong, they will just scoff and say "i have been doing this all my life so you can´t teach me anything"

@altuber99_athlete

3 жыл бұрын

@@PonaHD ElectroBOOM said some things right and other things wrong. Here’s one example, said at least two times: 10:54 Nope, the voltage across two points in the presence of a time-varying magnetic field is not unique. Theoretically (if you’re computing the induced voltage), the induced voltage depends on the path taken to compute the line integral of the electric field. Practically, it depends on how you position the cables of the probes, as Lewin and EB showed in their respective videos. You may say “it’s bad probing”, but I’d reply the following. As was demonstrated in the videos by Lewin and EB, voltage depends on the two points as well as the path. Now I ask you: “what’s considered the correct path to measure an open-circuit voltage, and why?”. I think the answer is: there’s no wrong path, all paths are correct. 11:48 Wrong. There was *always* two different voltages across the two points. Again, voltage depends on the path taken when computing the line integral of the E field. What you claim to be "the only voltage between two points" is actually the voltage assuming a particular path; assume another path and you'll get a different voltage. --- Here's another example: 8:41 In the circuits being studied at this timestamp, certainly the RL circuit with the switch and battery acts as one winding of a transformer, and the circuit with the two resistors only acts as another winding of the transformer, so EB's explanation is correct here. But what if instead of creating the time-varying magnetic field with the RL circuit we instead create it with a moving permanent magnet? I wouldn't consider the magnet as a primary winding of a transformer, would you? So in this case we can no longer consider the circuit with the two resistors as the secondary winding of a transformer. So EB's explanation is no longer valid.

I’m sorry to say that Veratasium’s video on how electricity moves through wires and also your discussion with him on the topic, helped me immensely.

7:12 thats good one.

It was an excellent demonstration of the importance of considering all the details in a scientific experiment. In the demonstration, the hypothesis is raised that the consecrated Kirchhoff's Law could be nonsense, depending on the side where the instrument that measures the same induced voltage is positioned - an obviously absurd hypothesis. If the measuring instrument (oscilloscope) is to the right or left of the same circuit, the voltage reading should be the same - but in the demonstration it did not occur. Thus, the hypothesis that the said Law would be flawed was proven. The layman certainly went unnoticed that in both measurements, right and left, the circuit was not the same. The circuit, in fact, is not only what the demonstrator draws, but also the wires, cables and the internal impedance of the oscilloscope should be considered. As it is electromagnetic induction, any opening between wires will have voltage induction by the variation of the magnetic flux that surrounds them. The measuring circuit, to be the same with the instrument on the right and left, should be what was drawn by the demonstrator at 12:04. Soon after, he shows in practice that he did not follow what he drew; leaving again a new half turn wire near to the experimental loop over the magnetic field generator. It was an excellent joke of illusion. Thus, the hypothesis of failure of Kirchhoff's Law can not be confirmed.

Being an accomplished physicist does not preclude him from being wrong.

@MarkTillotson

5 жыл бұрын

But he happens to be right. Its not hard to see that inducing current round a loop means the voltage also goes up round the loop one-way, so can never sum to zero.

@andrei-lucianserb1771

5 жыл бұрын

Being a youtuber does not mean you know how to teach. The professor was giving a lecture to students, and showing them how not knowing the limitations of Kirchhoff, will produce wrong results. He made an experiment... he did not take the limitations into consideration (he did not correct the result by use of clever probing)... he obtained the wrong result... he showed his students this fact... his students now remember that the limitations need to be taken into consideration and do correct measurements or whatever. That is all. All these people on youtube showing how the experiment should have been done, are completely missing the point of the experiment.

The Wikipedia article on Kirchhoff's circuit laws explains this under Limitations: "The current law is dependent on the assumption that the net charge in any wire, junction or lumped component is constant. Whenever the electric field between parts of the circuit is non-negligible, such as when two wires are capacitively coupled, this may not be the case. This occurs in high-frequency AC circuits, where the lumped element model is no longer applicable. For example, in a transmission line, the charge density in the conductor will constantly be oscillating." "On the other hand, the voltage law relies on the fact that the action of time-varying magnetic fields are confined to individual components, such as inductors. In reality, the induced electric field produced by an inductor is not confined, but the leaked fields are often negligible."

Your "noise" measurements are the inductance of the two wires in parallel and EMF induced into the circuit and the untwisted portions of your lead. Reason why it differs is they are in different positions one time closer, another time farther away, or other times not totally parallel with each other. In order for you to get an accurate reading you should use shielded leads from point to point or have your untwisted leads, 90 degrees from the measurement point. And if you really want to get picky, the probe itself will affect your measurement as it becomes part of the circuit. Because, depending on the frequency and voltages being measured, you can introduce capacitance or attenuation. I see what the professor is saying... when a circuit is being effected by EMF due to the circuit component characters, wire and connection resistance, until the EMF finally peaks, the circuit will behave and measure differently in different spots and will not equal zero. Depending on the placement of the EMF and the measuring devices you can get, either a positive or negative peak. You can see it in your noise measurement, those ripples are the varying voltages until the circuit stabilizes. Due to each component characteristics and connecting wire length the circuit at times, the total voltages will not equal zero. In addition, EMF waves are formed in the circuit which can be out of phase until the circuit "catches" up. And you also have angular velocity, field flux, stray field and cross lines to account for until the field stabilizes. Plus, just arbitrarily setting the circuit over the coil doesn't allow for accurate readings... When the law was written, they did not understand I-V characteristics, nor could they measure it or the circuit accurately. Plus you are measuring with a single scope... measure it will multiple scopes and compare the timeline of the voltages measured in the circuit and you will see.

You just invented Polite Roasting

@dirt616

5 жыл бұрын

He lives in Canada, eh? :D

@tylerhaley6301

5 жыл бұрын

Electric Blanketing, then?

@triffid0hunter

5 жыл бұрын

That's been a staple of good science since forever..

@TheXalos

5 жыл бұрын

Like a true Canadian!

I watched that class a couple of years ago and I found it very weird. I assumed he was talking about some advanced definitions and that the model of the "imaginary" inductor as a voltage source was a way to make KVL work out for induction machines. Now I feel so much satisfied with your reasoning ♥. Also I like to imagine the straight wire as a collection of tiny inductors in series, even the resistor itself acting as one, so that is NOT ok to assume 0 voltage drop just because the resistance negligible

Hmm...that is the basiscs of everthing: the ppotential difference as Voltage is only valid in a electrostatics, where the electric field is concervative. I think, this is tought in the very first lessons of every electrodynamic lecture.

WoW ! - I feel like I'm watching two gods fighting each other on mount Olympus and I have a BSEE degree.....

1:20 everyone. Imagine this world if just more people had Mehdi's scientific and philosophical humbleness

@akshatsaxena1431

5 жыл бұрын

@@therealb888 that's racist

As a medical student I have no idea what I'm doing here lol

@RebornRegal

5 жыл бұрын

It’s the mystical power of his eyebrows 😂

@bebeKoRider

5 жыл бұрын

you are not alone dude..hahaha

@mohammedaziz5496

5 жыл бұрын

😆 well you did learn something!

@nanoblast5748

5 жыл бұрын

Same.

@fadetounforgiven

5 жыл бұрын

When you have to use a defibrillator this might come in handy.

Explaining the path dependency of the voltmeter indications in the Lewin experiment isn't a trivial matter. To do so requires us to consider the role of electric fields in establishing uniform current flow along the closed secondary loop. In Lewin's experiment both conservative (irrotational) and non-conservative (solenoidal) electric fields act concurrently together along the secondary loop path. This is not arbitrary but occurs out of physical necessity. The induced solenoidal electric field is the primary agent of current flow. The conservative (quasi-electrostatic) electric field arises naturally in response so as to moderate uniform current flow everywhere along the secondary circuit path. This concept probably isn't on the radar for most of us, nor is it normally an issue in typical circuit measurements. We expect that a voltage observation made under low-to-medium frequency conditions is independent of the measurement path topology. When we connect a voltmeter across the secondary terminals of a 50-60 Hz transformer we would normally be confident that irrespective of how we position the voltmeter, we can trust our measurement. We aren't concerned with the conditions along the secondary winding itself. At higher (radio) frequencies we might exercise more caution with our "voltmeter" setup. Under low-to-medium frequency conditions the external electric field in the space between the transformer terminals determines the voltmeter indication. This external field is conservative. The voltage indicated at the open secondary terminals appears as a potential difference (PD) whose value we equate with the underlying emf. In the Lewin experiment we are actually considering what happens along the single turn secondary winding proper. There is no unique terminal pair where emf may be observed. As Dr Lewin notes, there will be a negligible resultant electric field along the interconnecting conductors which comprise most of the secondary loop. The greater part of the induced loop emf will be concentrated across the discrete resistor bodies with little appearing elsewhere. There is negligible resultant electric field along any inductive element winding carrying electric current - time-varying or otherwise . In the Lewin experiment there is a clear dilemma with respect to Kirchhoff's loop rule - the algebraic summation of voltage drops encountered in a unidirectional traversal of the closed secondary circuit loop is not zero. One needs to reflect on the meaning of terms like voltage and potential difference. It's worth noting that in electrical engineering terminology there is an accepted distinction made between voltage (electric tension) and potential difference - as may be found in the International Electrotechnical Commission (IEC) glossary of definitions. Some experts argue that if we consider only the conservative electric field components encountered in a traversal of the Lewin secondary circuit then Kirchhoff's loop rule does apply - since only scalar PDs are included. This latter view allows one to always validate KVL, irrespective of whether or not there are non-conservative induced electric fields present. This approach of "ignoring" the induced electric field component along the the secondary circuit loop might seem a misdirection. It's not clear why this is done other than stating that KVL applies only to conservative fields. As mentioned earlier, the electromagnetically induced electric field is the prime agent of current flow in the secondary circuit - the conservative electric field is not. The latter arises from the redistribution of surface charge density gradients along the circuit path in response to the physical imperative for both charge neutrality and compliance with Ohm's Law within the conducting medium. The view that Ohm's doesn't apply is inconsistent with explanations typically found in standard texts on Electromagnetic theory. David Griffiths text "Introduction to Electrodynamics" is a useful source in that regard.

Studying electrical engineering and watching your videos is the best combination

8:53 Dr. Lewin ended up not being a nice guy

@anantapadmanabhmyatagiri

3 жыл бұрын

@@outros5062 is it real

@user-md2ds2qh5i

3 жыл бұрын

@@anantapadmanabhmyatagiri you have internet. Try look it up. As far as the time goes, it is real.

@aasimali6937

3 жыл бұрын

@LonerWolf Patriot your reply made me laugh so hard that my ribs are paining now.

@alkalinepotato7972

3 жыл бұрын

He's a damn good physics teacher..... that's it! He's not a good person at all, just watch his interviews( search physics wallah walter lewin interview)

@Gunbudder

3 жыл бұрын

Damn, its like learning that Conway is a raging asshole who hates everyone and everything (especially the thing he is most famous for).

Why don't you churn out a thesis paper on this?

@DrummerRF

5 жыл бұрын

Because there is no dispute. All he did was replace the changing magnetic field with a transformer to make kirchoff's laws work because you can remove the magnetic field from the circuit. Thats nothing new

@Pknuckles1804

5 жыл бұрын

Some of the biggest idiots I know have doctoral degrees.

@CANOOB18

5 жыл бұрын

Because he isn't proving anything new, like he said most of science agrees with him but Dr. Lewin does not (but he didn't write a paper on it), so simply he's disagreeing with Dr. Lewin's disagreement with this law in physics.

@Jesse__H

5 жыл бұрын

that's all well and good but perfectly acceptable and _useful_ papers have been written on less. Science needs rigor, and a paper isn't pointless just for confirming something widely believed to be true.

@SeanHodgins

5 жыл бұрын

@@DrummerRF The argument is that there is a "hidden" inductor created through the measurement device, is it not? Which is why this is up for discussion in the first place. Proving that through math and experimentation surely could have a paper written on the results. Doesn't necessarily need to be a thesis paper.

Absolutely agree with ElectroB! Thank you for the thorough analysis!

What a legend man, I only understood half of what you explained, but I could tell that you were serious about it!

Dr. Lewin is displaying behavior far too common in the veterened engineering academics in that he clearly believes his knowledge and opinion is higher than anyone else. It is an unfortunate side effect of hubris in this field and I've personally experienced it in many professors. Simply in the way he responded to your comments, insisting that any argument is the result of no education and only his video and lectures can educate you, all the way to that last clip you showed where he reveals that every other author and professor disagree with him and yet they're the ones that are wrong? I recall a professor refusing to allow us to use Thevenin's equivalence when analyzing BJT circuits simply because she didn't like it. Every single online tutorial, university, and textbook insists on its use over 8 KVL equations but she didn't care because her opinion with gospel. Knowledge =/= education and that's incredibly important to keep in mind. You can have all the knowledge in the world but if you don't or can't question that knowledge then you're not well educated.

@drunkenhobo8020

5 жыл бұрын

" insisting that any argument is the result of no education and only his video and lectures can educate you, all the way to that last clip you showed where he reveals that every other author and professor disagree with him and yet they're the ones that are wrong?" Sadly sounds like the attitude you get from the likes of anti-vaxers and other conspiracy theorists. Even really intelligent people can fall into this trap.

@leocurious9919

5 жыл бұрын

Very good point. You can get a nobel prize (in STEM that is) but still end up talking nonsense.

@Riyu-san

5 жыл бұрын

Pretty insulting how he approaches Mehdi's request. Theres such a thing as confidence in science, but there is also blatant arrogance.

@gordonlawrence4749

5 жыл бұрын

I was lucky. When I changed career (I got bored with electronics as a profession as it takes 2 hours to design something then 8 months to do the damn paperwork). Several of the lecturers who were international leading experts in their fields said roughly the same thing: "This is my educated opinion, there have been many other educated opinions over the years that have been ultimately proven to be wrong. Remember the same is true of my opinion - just because I have a PhD does not mean I cannot be proven wrong at some point in the future." Basically we got marked on how many differing opinions we engaged with and how we analysed the evidence. In my dissertation I even got my supervisor questioning parts of his own PhD thesis.

@tonybp

5 жыл бұрын

Reminds me of medical academia. Most doctors today keep treating patients with medication that just makes them worse. Diabetes, for example. Countles and countless of cases where it's reverted by change in diet but they refuse to even take a look at it. Makes you wonder if theres a big pharma mafia after all. Fortunately there are more and more doctors leaving their ego at the door and raising their voice.

Dear Mehdi Mercury, I am (was) an electrical freshmen. After watching all your videos over the weekend, I decided to switch to Business & Management because I can no longer solder or plug in something to the outlet without imagining sparks.

@therealb888

5 жыл бұрын

Lol

@GAMEOVER-yy6zj

5 жыл бұрын

Well that's a negative effect.

@AuxiliaryPanther

5 жыл бұрын

Don't worry, this panther will carry the EE torch.

i like this way of experimentally trying to prove someone wrong. It's a nice and a humble way to disagree with someone of such high caliber.

Well, you very ably guarded the principles we(i say we for the viewers), have learnt in our science and engineering subjects. Keep up the good work! Would have loved to watch your videos growing up. Would have definitely helped to score better!

From Maxwells equations, the electric field E = minus grad V minus derivative of magnetic vector potential A. Obviously, mathematically, the sum of grad V around a loop is zero (~V2-V1+V1-V2). The question is, does the voltmeter measure grad V or E or something else in portions where A matters. It clearly doesn’t measure grad V, because the result depends on how you position its leads. The magnetic field affects the leads of the voltmeter and induces an additional E, thus current, inside them, which depends on how you position its leads in this magnetic field. The additional E is given by the rate of change of the total magnetic flux (magnetic field times area) through the closed loop formed by the meter leads connected to some circuit element. So, even if your leads follow the wires of the circuit, when you flip their position perfectly, grad V changes sign, while the additional E doesn’t flip sign. So, to eliminate it, the loop of your meter leads have to be parallel to the magnetic field (zero flux).

Where we you when i was studying? That's some beautiful explanation.

Thank you for contributing in the peer review process.

10:03 I love how he says " half-e-Vee" thats the Pinglish (Persian/English) translation of "half of V" . I love it because I do the same thing when I'm doing circuit analysis... add lots of farsi profanity.

9:56 "Why did we read 0V across the sense lines?" Because the path is different. At 9:26, your measurement loop encircles the flux, and the scope’s resistance allows a a path for the current to flow which arises from the induced emf from that flux. At 9:40, you’ve arranged your measurement loop such that it doesn’t encircle any flux, so there is no induced emf in that loop. In both cases, your scope is responding to induced current caused by the flux change thrugh the loop it forms with the probes and the wire arc. In the second case, there is little to no flux passing through the measurement loop as it doesn't encircle the solenoid -> no induced current -> no measured voltage. at 9:47 you find that you can get different results depending on how much flux you enclose. I can draw a picture if this isn't clear. 10:03 "If the voltage here is +V" But... It isn't. There isn't a localized potential difference there. Your previous measurement of +V depended on the path. Then you changed the path. This is covered in Belcher’s notes in the second video. But my intuition with this one is still shaky... Faraday’s law specifies that in the circle strictly around the loop, not including where the probe wires diverge, there is still am emf of 1V. In this particular circle, the impedance is high so there would be no resultant current across the gap, but how should we think of or visualize this EMF? imagebin.ca/v/4Qi4j6Awhq4w

@bamnasitis775

2 жыл бұрын

This all sounds like simple oversight? I saw the problem immediately with the way the sensor wires were arranged at time of sensing, almost seems like he's intentionally trying to fool people. A magic trick..but terrible

I sent this to some of my science teachers, im curious of what they are gonna say about it. You have all my support👊

Thank You Sir Engineer. You kept me even more curious in electronic world. I am so amazed with your videos. I hope to master all the basics and to starts doing advance.

I know nothing about this yet i enjoyed it thoroughly :)

@knowledgeispower604

3 жыл бұрын

Yeah me tooo I don't understand either since I got my masters in maths but still is enjoying it

Kirchoff's Voltage Law always works under one of two possible conditions. The first condition is that you wait long enough for the system that you are measuring voltage from to stabilize, or alternatively that it is a lumped parameter system (this would assume that the wires connecting components are negligible). The concepts explaining why this is so are summarized under the topic of transmission lines. With the help of the telegrapher equations, derived from Maxwell's equations considering a source-free space and the transmission lines that carry the signal, one can analyse the response of a signal in a circuit looking at it as a wave that travels at a fraction of the speed of light. This fast moving signal does not behave according to Kirchoff's voltage law until it has reflected and super-positioned onto itself sufficiently many times to stabilize to the expected Kirchoff's voltage. In other words, Kirchoff's voltage law is not wrong, it's only wrong to apply it to non-stabilized circuits or with non-zero length lines (which would not be a lumped parameter model) between components. With regards to the measuring of two different voltages between the same two points I completely agree with ElectroBoom. Not even at the fast speeds of waves traveling on transmission lines, given no reflections, will you be able to measure two different voltages at the same points. This has less to do with KVL and more to do with simple equa-potential of a point. The potential difference between two points in a medium, from Maxwell's equations, can be defined as the integral of the Electric field between the two points along some chosen simple path. Now, in the case where the B-field is changing, you can simply treat the total E-field as the sum of the regular E-field and the induced E-field (which is the partial time derivative of the magnetic vector potential) and voila, you have a net E-field from which a specific potential difference can be calculated. Having one equation and one unknown implies, from simple mathematics, that it can definitely be solved.

As someone uneducated in the field, I came to the same conclusion before you finished talking. I would love to learn why you would be wrong as I currently don't see it. Your arguments make perfect sense to me. The probe wires are part of this experiment when it is setup like this.

@skonkfactory

5 жыл бұрын

I'd go a step further and say that this is one of the cases where the fact that components are not, in fact, ideal, mathematical abstractions of components comes into effect. The wires have resistance and inductance.

@berni8k

5 жыл бұрын

I came to the same conclusion already when watching Dr. Lewins video. A wire going trough a magnetic field can't just be assumed to have zero voltage. No matter how low its resistance is, it will always have some inductance that reacts to the field. I could see however that looking at it from a theoretical point of view one could come to such an conclusion. In such theoretical examples you can never include all parasitic effects because the whole thing would just become a mess that literally takes weeks to calculate my hand. Its easy to miss a single significant parasitic effect and still have the math work out and seam logical. While on the other hand me being an engineer who deals with practical problems i know that a trace on my circuit board is not a perfect ideal connection between two nodes. I know from experience when a SPICE cirucit simulation behaves strangely that i need to model in some non ideal or parasitic effect. I have been bitten in the ass before by "simply ignore parasitics because they are so small they don't matter", my circuits didn't work how i wanted and every time it happened i learned how that particular parasitic effect is important and how to include it into my design process. You can't remove parasitics by simply ignoring them, you can only understand them and design them in as part of your product.

@megamixa

5 жыл бұрын

@@skonkfactory Even if the wires were ideal with zero resistance, there would still be a voltage across them. There isn't a voltage drop being measured across the wire. There is a voltage induced in the wire due to magnetic induction. If the wire were ideal, it would just give you a more accurate reading. The mistake that was made was not treating the circuit like a loop, but instead as separate parts. If you were to do the same with a transformer, you would conclude that KVL does not apply since the voltage applied is much higher or longer than the voltage read. But we know better since the change in voltage is found by measuring the coils.

@skonkfactory

5 жыл бұрын

@@megamixa Right, exactly- the wires have inductance (specifically, mutual inductance with the driving coil).

@skonkfactory

5 жыл бұрын

@@megamixa An ideal wire would have zero loop area and zero mutual inductance. It would literally be a circuit node of zero dimension.

Why am I finding my Physics Guru 8 years after I left my school. Absolutely brilliant demonstration man.

I am currently reviewing for my BSEE licensure exam. It leads me to this guy.

Mehdi is soo near to 2M...

@alanwolf313

5 жыл бұрын

He is a electronics channel not chemistry how can he be near to 2 moles?!

@shubhampreetsingh8630

5 жыл бұрын

@@alanwolf313 hahaha

@BadAssDownUnder101

5 жыл бұрын

And every single one of his subscribers is probably a uni student

@midhunterx

5 жыл бұрын

@@alanwolf313 Lol, That's BRILLIANT!

@user-kg7ii6if7d

5 жыл бұрын

@@alanwolf313 M actually refers to the concentraion c , M = Molarity

Every wire in a practical circuit may be considered an ideal resistor and inductor, no matter how short it is or how low resistance it may be.

I am with you. the probing circuit for me is similar to a eddy current measuring device for metallic tubes and rods. There are two coils in series vice versa winded to cancel the voltage out. that is then done two times at slighly different spots in differential measurement to make all voltages cancel each other out, as long as there are no bad spots in one of the two dual coils around the probe. it is somehow double differential style measurement. i hope i didnt misunderstand a thing here. i once builded such a thing and its a very cool circuit. by adjusting all measurement gains it is easy to measure tiny bad spots with an not so good handmade winding.

I am currently a diploma student in Electrical Engineering and I argued with a BME tutor at my technical University which I am currently a student at. So the argument was about AC and if it was stored or directly supplied to the grid as it was generated at the power station. I was surprised that he didn't have any idea and was debating blindly proving me wrong when I was actually right. Although he is a Mechanical Engineering tutor, he still should have known about Electricity and how it is generated and transmitted. What I am trying to say that holding a higher degree or qualification doesn't give you a position to judge others as wrong and proclaiming you are right, it's the knowledge with facts and the principal or law of science which you can use to prove something right. Kudos to you Mr. Mehdi. Respect also goes to Mr. Lewin.

@trevorkearney3088

4 жыл бұрын

Sure, a higher degree could be immaterial as you have noted and experienced. The relevant technological field of knowledge is a key factor. If the debate is about the facts of electromagnetic theory, who would have a clearer understanding of the physics of the matter in this case? In his second follow-up video on the same topic, ElectroBOOM draws heavily on the advice of another MIT physics professor - Dr John Belcher. Lewin and Belcher were colleagues at MIT. I've nowhere seen any comment from Dr Belcher disagreeing with Dr Lewin. BTW, hopefully you argued that AC power is immediately applied to the grid at a power station. I'm happy to discuss the matter of Lewin's demonstration further if you wish - from the Electrical Engineering perspective.

@chetankrishankumar4152

4 жыл бұрын

@@trevorkearney3088 Yeah i did. I explained it to him carefully that Ac is immediately transmitted to the grid. Well if you could email me Mr. Lewin's demo here at chetankrishankumar@gmail then that would be great. I am still a student and your insight would be greatly appreciated.

@trevorkearney3088

4 жыл бұрын

@@chetankrishankumar4152 I'll email you shortly.