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!
This really belongs to the positive sides of internet, I can attend classes from MIT from my home in Sweden for free. Let's forget about all the downsides of internet, at least for now.
I start getting why the MIT is so prestigeous. Professors like you are capable of perfectly explaining something to the students without confusing them. I am currently studying electrical engineering at the Technical University in Vienna and here are the students the ones, that have to understand stuff out of books instead of listening of such great lectures. i guess everyone has it a bit different and their way of learning may vary, but the finishing pount is the same for everyone. thank you for sharing your knowledge in your unique way.
Not necessarily the case. First, books will always teach you extra stuff, you can definitely graduate from pretty much any University if you understand the lectures, but those students who read always end up knowing much more, this is a truth that is often omitted, the main factor that determines the level of education is the student. The reason MIT students are so good is because it is damn hard to get in, thats pretty much the only thing prestige does to a university. Keep in mind that prestige comes in great part from research and there are great researchers that are bad teachers, in pretty much every university you will always find some good, some bad, and if you are lucky some excellent teachers. As long as you have capabilities and will to always go beyond what is taught in class, you can always get an MIT level education, its just that if you actually went to MIT the world will recognise you more.
I was practicing for my Sat physics subject test, which in taking because it's an MIT entrance requirement. I didn't know an answer about emf and current, but started thinking and heard Walter's voice talking me through it, and figured it out. These lectures did make me
Remember guys you are not gonna use this physics in your real life, and they are just of no use when you will be 40 or 50 years old, unless you choose to become a professor. I personally used to hate physics but now I love it. Thanks to teachers like walter lewin sir and alakh pandey sir. But when you love somebody too much, it becomes a distraction. Be it a girl, or a subject.
@@godson200 it depends on what you wanna do, if you want to be a doctor than physics is distraction but if you really love something you must persue it, if someone loves physics then they must complete a p.h.d and go to research field, here even at the age of 90 you will be using physics 14 hours/day in your life, from teaching to research and writting papers, a subject is not a distraction, everything is a distraction if you don't want it.
Sir, at first I was very afraid about #Physics but now a days after watching your lectures , I can feel that physics is a theoretical and interesting subject. Thank you Sir. Love from # India... 🇮🇳🇮🇳🇮🇳
I am a retired EE and CS engineer, having gotten my EE degree in the 60s. That being said, I am learning more from your videos, some of which I forgot, some I wasn't taught and some I never really fully understood. You obviously love your job and do a great job teaching. Right now, I am watching your videos selectively to get a better grasp of EM wave propagation, transmission lines and antennas. Thank you for posting these classes Professor Lewin! By the way, you probably should use less salt on your eggs. I know I have to. :-) I wonder what would happen if you poured some Gatorade into the distilled water. I think the answer is easy. I have to avoid the stuff because of the salt content.
Woooow mind blowing , man I love the way you teach in, where you connect everything together to help us understand feel the physics not memorize it !!! Thank you 👏👏👏
Dear Dr. Lewin: I have greatly enjoyed your lectures. My father was a professor of electrical engineering at VJTI in Mumbai. I have a Ph.D. in Mechanical engineering. Today at the age of 70, I still enjoy clarifying my fundamentals. Your down to earth and experiment based teaching is lucid and profound. My recent calibrations: Light travels 30 cm or 1 ft in 1 nanosecond. So a 1 GHz computer cannot have its primary memory more than 6 inches away!! 1 coulomb charges 1 m apart have a Force of 1 million metric tons!! That is 100m sided cube of water or 1 cubic football field of water!!
Walter Lewin saves! This is a core course in my bachelor's in electrical engineering degree and I started to hate it for the way it was taught. I started following Walter Lewin's lectures more than the ones in my class and well he achieved the impossible. He made me love the course itself and I've been solving problems and deriving equations with so much and enthusiasm! THANK YOU SO MUCH FOR THIS! THANK YOU SIR WALTER LEWIN! LOTS OF LOVE AND BLESSINGS FROM PAKISTAN!
Sir you are the hero of all students who wants to learn and love physics may be in life gives me the fortune to touch your feet (it is the way to show respect to our elders) you are my well wisher and a loving teacher of all time
hello sir, I've been attending your classes since last week and I've realized that there was so much in physics which i was not aware of , your classes made me realize that physics is very interesting and thought provoking.
Wow......you sir are AMAZING. I mostly had no idea what you were talking and writing about but as a 17 yr employed automotive technician that uses an oscilloscope literally daily, u were directly describing ptc and ntc style thermistors. A negative temperature coefficient thermistor or variable resistor is the most commonly style engine temperature sensor used in automobiles. Temperature up, resistance down. The lab scope is also used for issues pertaining to variable relector, hall effect...whatever sensors controlled by a transistor driver ( fuel injectors, ignitions coils, output solenoids, etc.....) Again....have no clue what you are saying but it is addicting and badass. I could listen to you all day.
Thank you so much for your lectures dear Prof. Walter Lewin. They are very inspiring. Please let me show some doubts about the last demonstration of the lecture: 1) The charge detected by the electroscope is due to a bulk conduction process through the soles or a surface conduction process over the soles, the shoes,... (or both processes)? 2) The charge detected by the electroscope could be an induced one by the charge created is the low surface of the soles during the scuffing? I know that a opposite charge is generated in the pad by the scuffing, but perhaps it can easily go to earth and have a net charge in the soles that could cause an induced charge in your body. 3) The electroscope null response when you stop the scuffing is due to the fact that the charge goes to earth through your body with the shoes. Do you think that can play a role the charge recombination in the interface between the sole and the pad? 4) It could be interesting and informative to repeat the experiment but placing bellow the pad a thick plate of teflon or fused silica to prevent the charge leakage to earth. Perhaps the electroscope do not discharge even when you stop the scuffing. Or may be the electroscope is discharged due to the recombination mentioned in 3) even when the leakage to earth is not posible. Thank you so much.
Hi Professor Walter, thanks for the fantastic lectures. I have a question: What would happen if you would touch de van de graaf while wearing your shoes? The charge of the VDG (the one you commonly used during your lectures) is only 10uC, so I can't figure out what would happen. I could come up with the follow (probably wrong) hypothesis: I assumed that you would experience a current from the VDG to ground, which would be limited by the VDG charge. The "tricky" part is that since the current flow is I = dQ/dt and Ohm's law gives us 100mA, it means the VDG can't provide enough current to keep that up unless it would get charged almost instantly. My (probably incorrect) conclusion is that therefore you would just end up feeling a initial shock, and if you could hold on the sphere after the shock, you would end up acting as a path for the current between the VDG and ground. Since the moving belt inside the VDG would start inducing more charge on the sphere, you would experience a (very low) current flow by the induced charge. All of this is assuming that the initial current could cause some muscle contraction but wouldn't harm you any further. Where did I go wrong? Once again thanks for the fantastic lectures, they are really unmatched. They make me love physics again and have been an excellent entertainment source every single day since I found out about them. Thank you!
Sir, this is Aryan. A huge fan of yours. If I would live near you, I would enjoy the whole day with you sir. Don't feel lone. I am with you sir, you will always be there in my heart. By the way sir, I am a high school student. I do love watching your lectures. I have just started with 8.02 and finding it very interesting but I have to skip some of them sir as I have not been a past learner of Calculus. So, according to you, what else could I do to rock my school with my physics knowledge ?
Dude just wait till class 11. In first month, you will learn all the calculus you need. Otherwise you can obviously go on watching these just for the love of it
showing the (non-linear) time regime impuls of resistivity is one thing, stating "not to trust Ohm's law" is a bit reductive (not to say blunt) ... we realized quite a lot trusting it (as we did with Newton's imperfect laws for instance) ... oh and though it's fortunate that resistance goes up with temperature, it's also necessary from a physical standpoint no?
Now where can anyone find a physics professor who measures the resistance of his footwear and scuff and produce charge! It just made my day. One Question:- Can we say that if the V-I graph does not pass through the origin then is a non-ohmic resistor?
+Anery Patel ha ha ha, I am sure I am not the only physics Professor who is a bit crazy. If the V-I curve is NOT a straight line then Ohm's law is not very useful. If it is a straight line but if it does not go through zero, Ohm's law is also useless. Ohm's law requires that when V = 0, I is also 0. However, a very interesting case is a resistor made of superconductive material. Thus R=0. There cannot be any potential difference over the R as that would give an infinite current. Thus 0=I*0 (consistent with Ohm's law). I can be anything. I can be hundreds of A. That's being used with maglev trains.
+Lectures by Walter Lewin. They will make you ♥ Physics. Okay. I see it now. Basically, for Ohm's law to hold good, V=IR must hold true, whatever the case may be(temperature being constant). And talking about the superconductors, how much ever voltage we apply the potential drop will be zero because resistance of the material is zero and so current will be infinite. I hope I understood it correctly. And I am sure that you are the craziest of all, boring into our skulls and fitting in the subject tight.
+Anery Patel We cannot apply to a superconductor any voltage as it would lead to an infinite current. In any circuit that we build to "push" current through a superconductor, the potential difference over it will be zero. >>>And I am sure that you are the craziest of all, boring into our skulls and fitting in the subject tight. It's my way of making all of you ♥ Physics. ! ! !
Lectures by Walter Lewin. They will make you ♥ Physics. But as far as I know to "push" the current through any material, a voltage or potential difference across its end is required. And if I don't apply any voltage or potential difference across the ends of superconductor, how can the current pass through it? And it is only then when we realize that the potential drop across the material is zero and we come to a conclusion that it has infinite conductance.
+Anery Patel There are various ways to create a current in a superconductor. One way that comes immediately to mind is that you start the current when the material is not yet a superconductor. The temperate is too high. You apply a voltage and you create a current. Now you lower the temperature and the material becomes superconductive. The current will keep going and the voltage over the super conductor becomes zero. I suggest you search the web to find other ways how very high currents can be created through superconductors in the LHC (at Cern) and in maglev trains.
Hello, thanks for the free lecture! I have a question: Why doesen't 𝛕 (tau the time between collisions) go down when the Electric field goes up? Why does it stay constant even though we applied a force to the electrons and they now are accelerated? Thanks!
I suppose it's because as was shown previously the effect of the electric field is almost entirely negligible when compared to that of temperature, and either way the time an electron takes to crash against a particle is probably the average one, so if the electric field pushes some of the electrons towards crashing maybe (and I mean maybe) it will then prevent other electrons from crashing somewhere else, meaning that its effect on 𝛕 ends up being cancelled
3:52 Drift velocity v{d} MUST be like ∆v, as ∆v=a∆t, and ∆t here means practically the same thing as τ. One caveat: the m in F=ma here is called EFFECTIVE MASS (according to wiki). _Drift velocity_ v{d} _is the average velocity attained by charged particles in a material due to an electric field._ _The drift velocity of an electron for a unit electric field is called the mobility of the electron._ _It is the average velocity acquired by a charged particle (like an electron or proton) in the body due to an electric field._ _Relaxation time_ (𝛕) _is the time gap between two successive electron collisions in a conductor._ ∆v _is the velocity attained by an object due to an acceleration._ ∆t _is the time gap between two successive changes in velocity._ _I think it's logical to assume these are kinda the same, but if you've got other ideas, plz share._
Hello, I cannot understand why I would be constant throughout the circuit when considering the series of resistors. I mean, after going through the resistor, the current should increase or decrease, not stay the same. Right ? Is it because of charge density of the material, and that therefore if localy a change in speed takes place, it will spread to junctions ?
Professor I have one question. Superconductors have zero resistance. Applying ohms law we get I=V/R Since R is zero Current should be infinite But what is infinite current? And if there is no infinite current how much current flows in a superconductor?
Hello sir! At 6:17 you derived the speed of electrons in that conductor. Then how come current flows within just the flick of a switch? Thank you, sir.
Hi Sir when you are doing scuffing experiment , at that time you are wearing shoes , then your shoes are rubbed against woolen cloth so your shoes gets charged right , not your feet ? ( i.e because your feet is not exerting any friction with the cloth )
@19:40 As temperature increases... the chaotic random velocity of all the electrons in the system increases NOT the drift velocity !! I got so confused ... misunderstanding the word "velocity" for drift velocity
Hi Dr. Lewin. In terms of the drift velocity is it understood that this is concurrent with the electron motion ? They are still bouncing all over and hitting atoms while also meandering in the direction the voltage field is pushing them?
Last experiment you showed that by scuffing shoe on a carpet we can produce electric charge on electroscope As the shoe sole has a greater resistances the electric current don't leak from the bottom of your feet charge on the electroscope and when you remove the shoes the resistance will you fall over great factor and there will be no static charge produce produces it will immediately flow through your feet that's what happened !
hi,thanks your lesson.May I ask that the voltage of the resistor is larger than that of the wire macroscopically, because the number of electrons remains unchanged, and the electrons need to pass through the thin tube at a faster speed to make the current equal, so a larger electric field is needed?
Sir, I have two questions, First, you said that resistivity increases with increase in temperature but when you heated up the air the electroscope showed more deviation which means resistivity of air decreased and both these statements contradict. Second, can you please explain the part that why the 2 billion resistance of the shoe is very low for the experiments you carry.
He is right, if forgot to discharge static charge it may follow by the electron dust (Just saw the news about passenger plane hit unknown object, I expecting the light bolt). 🛩⚡
