8.02x - Lect 18 - Displacement Current, Synchronous Motors, Explanation Secret Top
ฝัง
- เผยแพร่เมื่อ 13 ก.พ. 2015
- Displacement Current (Difficult Concept), Synchronous Motors, Induction Motors, Secret Top, How does it work?
Assignment Lecture 17, 18 and 19: freepdfhosting.com/885b570f3b.pdf
Solutions Lecture 17, 18 and 19: freepdfhosting.com/f55c880397.pdf - วิทยาศาสตร์และเทคโนโลยี
![[UNCUT] ฝันรักห้วงนิทรา | EP.8 (4/4)](http://i.ytimg.com/vi/RDYJYiDwsj0/mqdefault.jpg)
This website contains all my 94 course lectures (8.01, 8.02 and 8.03) with improved resolution. They also include all my homework problem sets, my exams and the solutions. Also included are lecture notes and 143 short videos in which I discuss basic problems.
ENJOY!
Hello Dr. Lewin, here you are talking about a website which contains homework and exam problems and solutions, however I don't seem to be able to figure out what is the website you are talking about. Would you mind helping me out?
Thank you!
It's my TH-cam channel
th-cam.com/channels/iEHVhv0SBMpP75JbzJShqw.htmlfeatured
Thank you Dr. Lewin!
Cheers :)
Lectures by Walter Lewin. They will make you ♥ Physics. ...sir while kicking the top why it is not going outward...eventhough surface is conclave....after some rotations why it's not gaining more energy... . ?
@@lecturesbywalterlewin.they9259 I am so much fascinaed by physics and the way you demonstrated it ..
thank u so muchh sir
Professor,
I find myself watching your lectures late at night when my brain is acting up and can’t sleep. I was always fascinated with how three phase motors worked and I love your lecture on it. You are slowly starting to make me love this stuff and slowly starting to get me addicted. I like to watch some of your highlighted lectures and shy away mostly on the more technical ones but as I learn more and more they draw me in. I don’t know how you’ve done it but whatever it is, it works!
This holy man understands the essence and meaning of lectures. Most of the teachers just read the math detivations from the fuckin' book out loud.
true dat
A truly suspenseful way to finish the lecture, I am at the edge of my seat literally. Thank you professor for another beautiful lecture.
+andrew morchik You are very welcome!
Thank you sir from the deepest of my heart. Physics is now no longer a burden, it is fun, a part of my life.
Its only because of you that now I understand and more than that enjoy physics.
Thank you again.
thanks for posting these lectures, they’re saving my grade right now and they are actually riveting enough to make me say i am starting to love physics (:
Looking at your lectures almost every evening... thank you Sir for your wish to diffuse knowledge!
Thank you so much for these wonderful lectures :)
brilliant series of lectures. contagious enthusiasm. nice nuggets of historical developments :)
you're a treasure person to the world!
Just listen to practical tips rendered by WL Sir at the biginning of next lectures.. 8.02x lecture 19.. I'm surprised at the practical exposure and passion of a physics professor. I have never come accross such a professor during my education.
Professor Lewin, I am not sure if you will read this message, but I just wanna to say thank you for your great class and the way you teach physics....you are the best one.
+sergio carrion Thank you Sergio for your kind words.
Mind blowing and eye opening lecture 😄
Ever since I started watching your lectures it has motivated me study physics, I like physics more than math.
Every time i watch your lectures Sir ,they make me love physics
:)
I am a mathematician and can not stop watching these lectures. :)
Sit am AM radio tuned between stations next to the top, and you will hear the pulses as the top moves about. The frequency of the tone indicates the RPM of the top.
Our exam was about until beginning of the 17th video. I finished 17th too. Tomorrow is the day. Now, all my friends that trying to learn physics from all around the world. Wish me luck and support me with your energies. Thanks.
All the best
Awesome video, professor... thank you very much for uploading these wonderful lectures.
Just a quick question... why do you draw the emf vs time graph a little displaced from the origin, does it have to do with the phase difference?
Thanks, professor!!
What an interesting idea to make electric motors of such an ordinary things! Thank you!
Our pleasure!
Professor, for the stator you have set up for the conducting egg/ring demonstration, how do the windings go?
It would make sense if the windings go all the way around in circles across the diameter of the stator, as then they would produce magnetic fields that match the preceding explanation, but it seems that they are wound like a toroid instead, which would not mainly produce magnetic fields inside the circular core only and minimal magnetic field at the center, and the field would also be oriented differently.
at min 32, you said due to magnetic field change there should be eddy current, but we know that magnetic flux over a closed surface is zero, therefore change of magnetic flux must also be zero. thus there shouldn't be any emf and neither is current.
magn flux through an open surfaces inside conducrtors is not zero.
@@lecturesbywalterlewin.they9259 first, thanks for the reply. lets consider a solenoid which is squarish and a solid cube. you create a changing magnetic field but only in magnitude but not direction. there is not many option as to calculating magnetic flux for solenoid which is approximately equal to [(area of the one square) x number of the turns]. whereas for the solid cube, there can be thought infinitely many surfaces(solenoid that have infinitely many turns for example or just a one square) because we are not obligated to pick a surface that includes all the cube. and only way to bound the whole cube is to pick a closed surface and for that case magnetic flux is zero and so is its derivative. In the end, there appears this problem as to according to what should we decide our open surfaces to calculate the EMF when the object is filled but not hollow as in windings
Excellent lecture 🙏🙏🙏🙏🙏🙏
Hey Dr. Lewin, if you don't mind me asking, I know I should be fascinated by how the nature of things really are, and I really am fascinated by how the synchronous motor works. Boy, I can say you've got me hooked to the playlist. You are very good at it. But what are the economic applications of a synchronous motor or phased current in the world today?
as I am not following all the lectures, can someone tell me what is the final adjustment (Dr Lewin mentioned this at 9:40) to Maxwell's equation? Or in which of the succeeding lecture did he introduce this adjustment? Thanks a lot
Just to make sure I understand, the energy of the spinning object is produced purely from the battery, or is there anything else which does work on the object?
Best lectures
Professor Lewin, your top is quite close in principle to the no-commutator contest motor that you had your students design. You get 90 degrees of attraction, then 90 degrees of repulsion. It's just the reverse ... the top has a permanent magnet in it and the coil underneath produces a magnetic field. In the motor the coil is the rotating armature of the motor and the permanent magnets are to the sides of the coil. But again you get 180 total degrees max of spinup on the motor without resorting to commutation.
It is told to me in my engineering education that physics is science and applied science is engineering. I can say, for sure , Mr Great Walter Lewin Sir knows all practical aspects of making things , including economic production aspects, better than engineering professors of top ranked engineering college of India. ... I'm not saying that Indian professors are less capable, mind wise. It is just that the capabilities are are not oriented in the required direction. That's not the fault of any individual. It's the fault of the Indian system, in particular education system. I'm a prey of the system....I am bit taken away...I have no intention of hurting anyone... It's time let's be 10% of WL Sir. Things will change drastically in India. I pray God to give him good health and strength so that we will be benefited.....Look , I'm selfish here. But let me be. 🙏 And big salute to WL Sir
Respected Sir, From your explanations ,I got an intuition that the slip in an induction motor depends on the geometry of the rotor.Am i right about it.Is there a way of varying slip without changing the geometry of the rotor.
Professor,
I cannot figure out how you have the 3-phase current induction motor wired. The solenoids look like they are wound perpendicular to the inside of the machine (where the egg spins), thus I would expect there to be very little magnetic field there. Am I misunderstanding something?
+James Dufour James, I do not recall the details of the wiring; I did the demo in 2002. However, my explanation about the rotating B-field is correct.
+Lectures by Walter Lewin. They will make you ♥ Physics. Okay, no worries. Thank you for always answering questions on these videos. Your lectures are wonderful. I found myself explaining to coworkers why a magnet is slowed when dropped through a copper pipe just the other day :)
Professor, I wonder does the coffee can have to be offset from the magnetic field in the beginning for the rotation to start? Otherwise there would be equal torques on both sides so what causes the rotation? How can torque on one side be stronger than torque on the other if the magnetic force is equal and the can is symmetrical there should be equal torques on each side? And as for the egg I also wonder how does the forces pushing it alternatively in 120deg offset cause it to rotate and not just move in the direction of the force?
Thank you professor, I love your lectures
Sir,
05:00, you have applied ampère's' l'aw and wire May be semi infinite but ampère's law valid for infinite long wire.
If you calculate magnetic field at point p by byoswarts law then it will be nearly half of ampere's magnetic field.
Then how can we use ampere's law ?
I found the Eddy currents explanation of the spin, really hard to understand. Due to rotating B-field, in which plane/directions Eddy currents occurs? Why?
I've got exactly the same question. Did you find the answer? Thanks!
Hi Prof. Lewin, First of all thank you for sharing your inspiring lectures. I've been following 802 for a while (not finished yet) and I have a little question.
You've introduced the magnetic force as the force experienced by a moving charge in a magnetic field and that's ok! :) But when coming to magnetic force between magnest or simply between an object producing a B field and an iron needle which physic model shall we apply? What is the link between the force experienced by a moving charge and the repulsion/actracton force bewteen two magnets? How do we estimate the force produced by a magnet on a different magnet? Still, the north and south pole of a magnet are issue of atomic configurations of the material?
Thank you,
From Italy
Lorenzo
very difficult to evaluate that force. It's very very geometry dependent. I do not cover it in my lectures. Use google or quora.
Thank you. I'll google it.
That's the "problem" with science and it's also what makes it interesting, the deeper your understanding you want to be, the more you realise that you do not understand. It's a never ending loop.
Dear Walter, Is there any way to calculate fringe field effect at 19:13?I would be very grateful if you could help me. I wanted it to calculate for my experiment.
use google
Sir, how is the conducting egg rotated in its longitudinal axis? What made so?
Professor, can you please explain why the magnetic field through the other two loops are two times smaller?
Cos(120) and cos(240)?
Are synchronous motor and induction motor two different things?
Did you place either a magnet or a conducting sphere/egg? I got confused and thought that you placed BOTH at the same time.
At the moment when magnetic field from one pair of solenoids reaches it maximum other fields must be two times smaller because they are shifted in phase by 120 degrees (look at the 3 phase graph).
Synchronous motor is a type of motor that rotates with the same frequency as rotating magnetic fields inside it. Induction motor is also known as asynchronous motor because it always would rotate slower than magnetic fields inside it so they different things.
Sorry for my english and that I'm not a Professor.
@@patryk_49 are you an electrical engineer? 😊
Looks like the secret top is no longer top secret!
:)
Hello sir... This is Aadi Bharatia from India, grade 10. I want to request you to upload a detailed video on the connection between electricity and magnetism through special relativity... I searched it up a lot of times on TH-cam and the internet, but didn’t get a satisfactory answer... Pls sir... if you could make such a video, it would really better my understanding of this force which we vaguely call “magnetism”...
Do MIT STEM courses have a lab component?
Sir, have you explained the working of transistors in any of your lectures?
no
Super.....
At 10:28, it should probably be the change in electric flux, professor!
SIr, Lorentz force is force in a current conducting wire situated inside a magnetic field. on the other hand, Faraday's law tells us that a changing magnetic flux will create an electric field. for an induction motor, the electrical filed will produce current flow, the current flow will produce magnetic field, the magnetic field will interact with the previous magnetic field and as the result of this interaction the rotor will rotate. My question is that, is the same phenomena is explained in two different ways by two scientist?
en.wikipedia.org/wiki/Lorentz_force
Thankyou sir,how can we create 3 phase motor sir.in our house we only have a single phase.
Greetings from India professor,, I was wondering ,, are the electrons inside a conductor carrying alternating current executing simple harmonic oscillations?
no
Whta do we mean by restrictive paths of eddy currents sir
Professor can you tell which resistor (the code) you used in the circuit of spinning top
I have no idea - this was 16 yr ago.
Lectures by Walter Lewin. They will make you ♥ Physics. No problem thanks for responding
South means positively or negatively charged? And what polarises it ? Is is the magnet via induction ??
question unclear. use google or quora
At 29:21, how did you find that the second coil will achieve maximum current after one-third of a period?????????
refer to the graph at 26:39
Hello sir. I have 2 questions.
1) In displacement current, are the electrons propagating through the space between capacitor plates?
2) Is there any difficulty in finding it experimentally?
I wish you have a healthy life!!
*displacement current is NOT a current.* Watch my 8.02 lecture about it or use google
Sir i have an out of context question. Its from nuclear physics. I tried google but it could not satisfy me.
After β- decay, the daughter nuclei has one more number of proton than electron and hence it must have +ve charge. But while calculating Q value of this nuclear reaction we don't take the positive charge into account. Why it is so?
Pls reply professor. It would be of great help.
β- decay, one neutron in the nucleus becomes a proton, an electron and a neutrino are emitted from the nucleus. Thus the element changes (it moves up one step in the Periodic Table). The atom is now a + ion. An electron is needed to make the atom neutral. Countless electrons are in general available to make that happen, but if it does not happen, the atom remains a + ion.
en.wikipedia.org/wiki/Beta_decay
Thanx professor it was really helpful
Does Faraday's law give us an insight into the steady state of the circuit because when DC supplied to capacitor current stops flowing without much of a time lag and whereas maxwell's equation deals with instantaneous situation?
Faraday's law is one of the 4 Maxwell's eqs. It ALWAYS works in ANY circuit with C's R's and L's, also with external B-fields. Faraday's Law runs our entire economy. It works at ANY moment in time, whether you have DC or AC.
Thank u so much
Sir if the capacitor plates are rectangular instead of circular can we get right ans by just replacing the area in dphai E dt to area of rectangle instead of circular plate
area of plates, dielectric between plates and distance between plates is all that matters.
Sir , In my 3rd pre-Final exam in my school , I got 1st position in my class But Sorry , it was not a perfect score , I scored 98/100 ........ But my Final exam will be on 7th of March and Exam center is some other school of my city and I will try for perfect score in main and final exam - which counts
:)
I think solenoid means a structure of continuous windings to direct B in particular direction. At 27:14 there is a significant gap between the two windings. How magnetic field gets directed in some direction and how can we call it a solenoid??
this is much more subtle than just 1 solenoid!
OK , thank you sir. here the solenoid action is to direct magnetic field in particular direction no??
it's a THREE phase current! watch the lecture!
thanyou sir for making us able enough to appreciate the real beauty of the subject.
just one thing....
dQ/dt confuses me. does the charge keep moving b/w the plates, making us write I=dQ/dt or is it that once the capacitor is charged there is no magnetic field which makes sense right?
If there is a charge Q on a capacitor, this Q can change depending on the circuit. dQ/dt is then the current in the circuit. Of course dQ/dt itself can change in time that means the current I is a function of time. .
thank you sir
but how are we able to write the displacement current as dQ/dt when the Q is only in the plate's vicinity. or do the charge fly in b/w the plates?
The displacement current is NOT a current. The name is a misnomer.
glad to receive the answer. thank you
:)
anything which holds charge can act as capacitor
Sir, at 17:54 min you tell the magnetic field will fall like 1/r inside a parallel plate capacitor. but the way the equation was deriving wouldn't it be falling in 1/R fashion
Listen more carefully!
>>>field will fall like 1/r inside a parallel plate capacitor. >>>
I never said that!
Sir, I couldn't understand the how does the eddy current can cause the sphere to spin. Can you please explain that? Thanks
Yun Heng I suggest you watch that part of my lecture #18 again (as I just did myself). Eddy currents are produced in the egg. Due to the Bxv force, B being the magnetic field vector and v the velocity of the charges (Eddy currents), there will be a torque on the egg. This torque will rotate and that causes the egg to keep spinning. The oblate egg ends up spinning "vertically" since that is the position with the lowest moment of inertia. tau=I*alpha.
There is something that I didn't get in this lecture.
The three-phase synchronous motor. If we have a three-phase current, than we can produce a rotating magnetic field. But how do we produce such a current? Should we manually rotate a triple loop? But then, we are transforming mechanical energy to the mechanical one, which is nonsense. Or do we obtain such a current from the power socket? In this case, how do we make it relatively shifted with a right phase in each coil?
en.wikipedia.org/wiki/Three-phase_electric_power
+Евгений Голиков
Power generation Plants , (hydro, thermal, nuclear, wind etc) produces three phase current.
and that is transported to sockets at home.
watch this Video properly he explained how three phase V or I is generated by three rotors at 120 angle.
Also whats wrong with converting mechanical energy to mechanical ? though that not the case here. But could be in a science project that students make at school or college. where they can generate power by manually rotating then converting it to electrical energy then elecrical enrgy converted into mechanical again with Losses.
not direct mechanical to mechanical like two gears
Professor Lewin explains multiple times in this course that an EMF is induced when we rotate a loop around its axis... but could someone clarify exactly what effect this has on the motor? What does this induced EMF actually do?
watch my lecture whe I discuss the basic idea of an electric motor.
Hello sir, in 12:05 I understand there is electric flux through surface in capacitor, but isn’t there electric flux from the wire itself as well ? ( aiming perpendicular from the wire, similarly as it was when you taught us the electric field from the charged cylinder - if that would be the case there would be more electric field lines penetrating the surface) thank you and I hope you understood my question…
electric flux trough the surface of wires through which current flows is not zero but it is in general so small that it can be ignored.
@@lecturesbywalterlewin.they9259
Thank you so much for your answer :) May good health following you for many more years, your lectures are helping me a lot!
I am confused... and yes I went to Google to try to heal that confusion, but I could not find anything. That bugs me out because it means I do not understand Ampere's law and I can't bear it!
At 4:00 , you calculate the B field at point P with Ampere's law. I thought that Ampere's law gave the sum of the B field on the whole closed path, but not on a single point!? In Ampere's law do you not consider the contributions of the rest of the wire? I thought that Ampere's law was for only for a dl element of the wire (cross-section).
On the other hand, I agree that the B field at Point P is B = mu_0*I/2pi*r. If I used Biot-Savart law (considering that point P is far from the capacitor plates) I would find exactly that, because it is a straight and long wire. Each element of the wire contributes to make that B field up at point P.
That means I have the wrong definition of Ampere's law. I need help!
does kappa even change dispacement current because it cancels every time as dE/dT= I/πr^2K epsilon zero
question unclear
If a ring is falling with its plane vertical, in a uniform horizontal magnetic field, will there be any potential difference between various points on its circumference?
there will be Eddy currents in the metal, thus there will be potential differences between various points.
@@lecturesbywalterlewin.they9259 thank you soooo much sir.
At 35:29, why did the conducting egg changed its plane of rotation?
www.physics.usyd.edu.au/~cross/SPINNING%20TOPS.htm
Ampere's law is applicable only if the electric field at the surface does not change with time ,how is it possible to have constant electric field as the charge(in motion) always produces varying electric field?
>>>Ampere's law is applicable only if the electric field at the surface does not change with time>>> *that is not correct.* Ampere's Law also holds with AC. If there are also capacitors in your circuit, make sure that you use Maxwell's version of Ampere's Law.
34:30 sir how rotating magnetic field kept the conducting egg spinning
if B field is constant it will slow the spinning conducting egg down. In the very speciall case of a rotating B-field (my demo) it can keep the egg spinning - try to reason how that happens or use google
sir....do flow of charges..or....free electrons in the wire or conductor perhaps....obey the Newton's laws of motion????
th-cam.com/video/PJqOaHBgr30/w-d-xo.html
Thank you sir....Sorry but i have watched Lectur no.9 and didn't find the proper answer to my question..can u please draw your attention once more to it{question}
Sir how eddy current and rotating magnetic field cause torque on rotor because both magnetic field due to eddy current and rotating magnetic field are causes same and opposite forces on rotor. Is this is right. Because I am in confusion after reading papers on working of induction motor.
it's easy to see that rotating magn fields cause torques. use google
Thanks Sir
26:27 Sir, shouldn't the plot of loop 2 be loop 3's plot and shouldn't the plot of loop 3 be the plot of loop 2? So shouldn't the plots of loop-2 and 3 change? thank you
nope
@@lecturesbywalterlewin.they9259 but otherwise loop 2 starts from 0 Volts. But it should start from a higher value than 0.because voltage is Vmax(sinwt) and this is not 0
Respected sir, at 10.28 u said "no electric flux passing through the surface" shouln't it be there is no change in electric flux because if we connect a battery electric field would be passing throught it....
I watched at 10:28. What I said is correct. Review your knowledge of the meaning of electric flux
I think that maybe in a parallel universe there is a magician called Walter who hypnotizes people with physics.
what is the divergence of displacement current density ?? is it going to be zero
en.wikipedia.org/wiki/Displacement_current
@@lecturesbywalterlewin.they9259 sir, I have already read the Wikipedia article and understood it, but unfortunately it doesn't clear my doubt. That, the displacement current inside the capacitor is constant is space but changing with time, so it's divergence should be zero inside the capacitor.
My humble request to you would be, if you could explain what is the status of the divergence of displacement current density inside the capacitor plates .
At 15:38 when you choose the flat open surface between the capacitor plates, why can't I choose my surface to include the whole area of the plates, e.g. like a light bulb?
Image: scontent-arn2-1.xx.fbcdn.net/v/t34.0-12/13015095_1037129163012582_1075484716_n.png?oh=25212cd92d662d7fe248b785ab1c458d&oe=570EEBB7
+lauroflorin You may choose any surface you like. The reason why I chose the surfaces the way I did was for educational reasons. Watch it again, and you will understand it.
But the way I chose my surface e.g. as a lightbulb (see link in the comment) makes the B always equal to I * μ0 / ( 2 π r ), whether I'm outside or inside the capacitor plates, so clearly something must be wrong
scontent-arn2-1.xx.fbcdn.net/v/t34.0-12/13015095_1037129163012582_1075484716_n.png?oh=25212cd92d662d7fe248b785ab1c458d&oe=570EEBB7
+lauroflorin Perhaps you did something wrong. I suggest you watch my lecture again, that may help you. For sure I did nothing wrong.
Lectures by Walter Lewin. They will make you ♥ Physics. Aha ! Got it, when I choose my surface to be a lightbulb, some E dot dA will be negative, leaving only the area of the closed loop in the end. And again, Maxwell/Ampere holds :)
Thanks !
Can I do any sum using basic faradays law?
question unclear
Sir, Whether the magnetic monopole were present in the early Universe ?
maybe - use google
okay Sir!! Well, Which side are you on ?
>>>Which side are you on ?>>>
East Coast USA
:) Now, I have Nothing :) *But I still have Something.*
You have my book and that's what you wanted. No viewers have my email address and no one has my home address. When I meet with people in Cambridge, I never meet at my home. I meet at a restaurant nearby. It's essential for my own privacy and security that my email and my home address are strictly private.
Maxwell House, Hey oh!
Sir,can you please make a video explaining induction motors and generators?In this video, you explained it very quickly which was very much less intuitive.You even didn't do any calculation about its rpm.
use google
Can you suggest any particular source?So far I have been confused, sir
you have to learn how to use google
www.explainthatstuff.com/induction-motors.html
en.wikipedia.org/wiki/Induction_motor
sir how eddy currents produce torque?
If B-field is constant it will slow the egg donw, in the case of the rotating B field (my demo) it will keep it going around. use google
A capacitor has no internal series inductance... -Ivor Catt
Ivor showed that displacement current doesn't exist and that a cap is like a transmission line, and the em energy is going back and forth, b cancels and e appears steady.
Maxwell added a term to Amperes Law. He called it "displacement current" but it is not a current.
Because of this addition he coud predict the speed of light
Hi Professor .....why is the electric flux through the flat surface 0 ??
it's NOT 0
@@lecturesbywalterlewin.they9259 I don't know.. am I hearing it wrong that you said in the lecture that ''there is no electric flux through the flat surface and hence displacement current is 0 at 10:27 minutes
@@poojaramesh1133 it is zero in that specific case. But that case is very special
Love you sir, how can make 3 phase from a single supply sir
not possible
@@lecturesbywalterlewin.they9259 Sir then how could we function trilling machine in home
This one is the most difficult so far
what physical meaning has the displacement current is possible to imagine it?what is really?
itis NOT a current - it's a misnomer.
Sir how there is changing electrical flux in between the capicitor plates didn't get the point.....
how many minutes into the lecture?
From 7:10 to 7:40
And also at 21:37 metioned that a changing electric field will indeed cause a current in between the plates
watch the lecture again. I explain this very well. I cannot add to the clarity of that lecture.
Sir at 7:15 the reason why "there is a changing electric field" in between the capicitors??
Oh ! this sentence was given in concepts of physics by HC Verma
Sir did nikola tesla sir invented this induction motor
Professor, please, you’d spoken about Franklyn, Faraday, Maxwell, but you never mentioned Tesla. Why is it so, sir? He is one of the inventors of 3phase currents and he invented the induction motor, the Egg of Columbus you show. Can you please tell me, my dear professor?
I followed the Giacconi approach.
Lectures by Walter Lewin. They will make you ♥ Physics. Of course sir. But you used to tell stories like the one when Faraday replyied “one day you will tax it”. I am asking you, why did you never mention Tesla? What is your opinion of Nikola Tesla, dear professor?
hi professor i wanted ask for quite a long time that in your lectures you have talked little bit about every scientist for their work in EMT but when you lectured about AC current you didnt even say a word about tesla so any reason for that? or was it just a coincidence? p.s i love you and your lectures ❤
Sir In India We use PAYTM not PAYPAL , you have account on PAYTM ??
no
ok Sir! I will join PAYPAL 😊😘
th-cam.com/video/wD5zfc1TZ0M/w-d-xo.html
Your pink arrow in the add in segment is pointing the wrong way
how many minutes into the lecture?
Lectures by Walter Lewin. They will make you ♥ Physics. In your later added part of the lecture at 30:30 all vectors point in different directions, where as a few seconds later in the original part all vectors are roughly pointing in the same direction.
Sir I really appreciate the extra work you did with rerecording this part just to help people undestand it
Why is electric flux zero at point p1
flux goes through a *surface.* flux through a point is always zero as it has not surface.
I mean for the flat surface containing point p1
@@rakshitsohlot7461 Do you see a potential difference between both sides of the surface through P1? And between both sides of the surface through P2?
Maxwell died in 1889, not 1789, no?
yes
hello sir I think you complete your PhD in astrophysics.am I correct!
incorrect
Nuclear physics
Use wikipedia
1 march 22
I'm pretty sure they usually rotate the magnets, not the wires. Because if you rotate the wires you have to have brush contacts, which will wear down and cause other issues, while when you rotate the magnet, you only have the bearings wearing down, which last a lot longer.
Sir , I am in a Big Trouble Since you had posted Solution of that Problem and Now , I'm daring to tell it *with that Super Method which you told us* , I don't know Whether I'm Wrong or Right........ In my Book there is a Question and for that I don't found it Works for me , Please Tell Why this Method is not Working *Is it Right , I found it doesn't work for Unsymmetry*.
.*Vader , Please Forgive me if I went Wrong*
solution Problem 24
*method 1 ALWAYS works.* The super method ONLY works if certain symmetry conditions are met. I will upload a video later today to mention that and to correct my statement that the super method always works - that is not true.
Lectures by Walter Lewin. They will make you ♥ Physics. *Vader , It was Good to Hear that What I was thinking from Yesterday is Correct* , Yesterday I was scared to talk about it you But Today I Spoke Courageously to you *Now , I feel very Relax that *Je Zoon heeft gelijk*
:)
Lectures by Walter Lewin. They will make you ♥ Physics. Sir , I don't Like Chemistry - *Very Bad Subject* "I Can't remember anything without proof" , *Specially that Organic and Inorganic Part of Chemistry* 😢😞😥