I wait eagerly for him to say ,'So first I want to demonstrate to you....'

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.

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

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.

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... 🇮🇳🇮🇳🇮🇳

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!!

I started studying physics to clear IITJEE but ended up falling in love with it

I LOVE HIS TEACHING

i discovered his videos now and they are helping me a lot in preparing for my medical entrance exam called neet in India. Thanks a lot lewin sir.

I'm legit crying at how much better this is than my *current* professor. lol

Sir, your lectures are a gift to humanity.

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!

Thank you Professor Lewin for all the great lectures and resources you provide! You are a true inspiration!!

Enjoying lockdown by your mind blowing electricity lectures💓

Would it be possible theoretically to give an electric shock to a person on the other side of the earth, if we had high enough voltage?

I find your lectures useful and inspiring. Thank you.

The beauty of ur teaching is how easily u convert complex things easy

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

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!

Love you and your lectures a lot sir they are making me love physics 💓 💓 💓💓 💓

Sir really your teaching skills are amazing , love from Bangladesh :)

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 ?

Hey Dr.Lewin, So is current in the sense of circuit analysis just a simplification of a vector for convenience sake?

Sir you are the legend of physics. These lectures are useful. I watched every lecture.

excellent explanation of Ohm's Law extended to encompass the world around us. Thank you Prof. Lewin

Hey almamater u r just phenomenal Loved ur experiments evry time u watch u learn even more with the dimension of thinkng being enhanced

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 )

Huge respect, sir i am really in love with physics because of you. Thanku so much sir ❤ love from india 🇮🇳

Congratulations sir ,for your biggest achievement. That you know.

An excellent lecture. Thanks for uploading it.

Thank you professor lewin for all your efforts!

Thank you sir to help poor Indian students in this situation by giving your lecturers on KZfaq.

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.

This was really helpful for preparing for my test. Thanks!!!

Awesome experiments, absolutely loved it!

This man is a legend. Please keep teaching. Thank you Sir!

I'm so glad that my teacher suggested me about ur lectures on youtube sir😊😊😊😊😊😊😊😊

Finally you changed your channel's profile picture!!!! GLAD TO SEE!!!!☆★☆★☆★☆★

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!

This is the answer to our lack of education problems. Get our most brilliant minds and make their knowledge free and universal.

Sir charge density(j) =di/ds and not i/s,why?

Love from INDIA 🇮🇳🥰🤗 Thanks for the professor Walter Lewin🙏for making us to love physics ❤

i cant express enough how much i loved this

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.

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.

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?

the drift velocity being a*tau, is a approximation right because between collisions the drift velocity is variable, not constant, right ?

Can you please tell me know what lecture in 8.01 covers drift velocity? I do not understand what tor (T) means. Thank you

Sir , if we connect a dc battery across a wire , why the current density is uniform over the cross section of the wire ?

I have Giancoli 4th edition which seems to be wrong for this. Anyone know the correct edition?

Why doesn't the water electrolyze in the demonstration experiment on decrease in water/electrolyte resistance with the addition of salt?

Sir I Love your lectures and it helped me to learn more abou physics

Could I find course 6 (of that complex resistor network) in MIT OCW

Professor I have a question...what would those SPECIAL shoes( worn by thief in the end) look like in order to make a working static gun from his finger?

Hello Professor,please provide the exact definition of series and parallel combination of resistors.

6:34 turtle and rabbit story still valid here wow

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?

So professor, at 4:45 we are assuming that the E field is same throughout the copper wire, right? Otherwise we couldn't be saying V=EL (where L is the total length of the wire and V is the voltage difference between the two ends of the wire), right?

Thank you for helping me go through my physics mock.

The graph 📈 is so good

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! y do u always pin some tools on the right side of ur shirt!

what is the substitute for ohm's law ?

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?

Really appreciable nice method love it

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.

I have been taking many mit courses during the lockdown and there are very few teachers like prof. lewin

THANK YOU SO MUCH SIR PROVIDING VIDEO, ITS REALLY VERY HELPFUL FOR US. I LOVE THE WAY YOU TEACH. LOVE YOU SIR W.L

What does scuffing your feet do exactly? Does it increase the resistivity of your feet, slowing the current, and allowing the charge to stay on the thing? If so, why does the resistivity increase? Is the temperature of your soles changing?

40:19 will the light lit on if the water is heated up and without adding salt?

Sir, since current is defined as the rate of transfer of charge from one side of the area to the other side ,so 'i' must depend on area also but the equation is just i=dq/dt ,how?

Sir, ur way of teaching is fabulous 🤓

Hi Sir, Does increase in voltage will increase the speed of the electrons or numbers of electrons in a conductor ?

If the drift velocity is almost negligible compared to the velocity due to thermal motion, why does temperature increase with current? Thanks!

3:40 What the drift velocity somehow follows from the acceleration from the electric field?? I dont follow

3:25 professor I have a question that why you have used F=ma for acceleration of e As I heard that mass of e changes by the relation m=m°/√1-(v²/c²) I have this confusion about it. Please elaborate 🙏

Sir , if I connect an n-type semiconductor to a Dc voltage source , will it conduct current easily ?

So maybe I am missing something, but I thought the E inside a conductor is always 0? In the case of the Cu wire is it only the surface e- that feel a force?

Professor, I am having a tough time visualising the E field inside the wire. At 4:49 Why is the E field inside the whole conductor a constant (1 V/m). Since the length of the conductor is 10m, shouldn't the magnitude of the E field inside the wire at different distances (from the origin of the E field) be different? Where is the origin of this E field actually?

45:53 isn’t it that even without the shoes, when one touches the Van de Graaf, he won’t be electrocuted, because even though it has high voltage, it still has a litttle net charge on the surface, so the high current (lets say 300000V/1000 ohms = 300 Amps) will take only a split of second and shoud be harmles? And after the charge is drained out, if you keep touching the VDG, it won’t have the 300000 voltage anymore since the VDG is actually a constant current source generator, and the amount of charge delivered is so small that is, again, harmless, am I right or not?

Say we have a 600 000 Km long conductor connected at some potential V. If we place 2 ammeters next to the terminals, which ammeter is going to move first and how long until the second one moves? Why?

Hey can someone help me out with a physics question. So Im studying the Current section, and that tells us how many charges are passing through the cross sectional area of a conductor right ? but how can that be if the electric field within the conductor is zero (since E= 0 (guess's law), inside there should be no moving charges because there is no potential difference)? shouldn't all the charges be on the surface of the conductor and not inside?

Dr. Lewin, could we not also say that a negative current (i

Where I can find explanation for the system at the end of the lecture? Please show me. Thank a lottttt.

Sir, why current is taken alway equal along resistor? Is electric field or drifting of electron is responsible for current? If current is energy isn't it used by resistors?

Teacher, can you tell me the reason why (25:25) at the beginning the current surged towards to a very high value? Thanks you a lot!!!

I have a question Prof. At the end, when you take your shoes off, you have very low resistance, so the current should be higher. But the electroscope shows no deflection. This implies that no charge flows through it. Where am I getting it wrong?

"Teachers who make physics meaningless are criminals" I can't remember it exactly , my level in physics is improving rapidly thanks alot Dr/walter

as a 9th grader i understood everything. u make learning so easy. thank u so much sir

how does it feel to hold a CAT fur in your hand?

Sir , why is Drift velocity = EeT/m not EeT/2m since it is the average velocity of electrons? Another question: Why T(tao) remains same when temperature and material remains same? The T is the average time of Collison of electrons and since the drift velocity is higher in higher E(electric field) the collison time would get shorter. But this is not shown in you derivation at starting calculating the speed of electrons and I Current

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 ?

he made me fall in love with physics once again.....

Can't Ohm's Law be effectively saved if we were able to define temperature for a substance as a function of current? Would that relation be reducible to some constant coefficient multiplied by a function? What would a temperature function of the current look like? What else would it be a function of?

Q - 1:00 as the electric field moves the electron from lower potential to higher potential it's should have a huge significant value of electric field ?

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?