dA is a surface element, explained at the beginning of the lecture. the lenght of the vector dA is the magnitude of the surface element (explained at 02.02), this has nothinf to do with forces, don't know where you see forces.. look again please..
@slimmerikje oh, he said that the book writes n*dA simply as dA. I assumed that n was the normal force? And dA is the surface area of that specific element right?
I was curious to know that are these topics like gauss law, biot-savart law etc taught in college in USA?
I live in India and study in 10th grade and we will be studying that in 12th grade though i and many of my friends have already studied these topics....
@Superdoerr he applied pressure from one end of the chalk at an angle to board (greater than 90 degrees from the direction) and with the speed of his hand and the friction produced from the board, it makes it skip (learned that in art class :b)
yes ye amazing conspiracy haha. Ive heard this topic 3 times n until now I didnt notice that every electric field at every point inside the sphere is equal to 0.
Great, I tested out of all my intro classes and I feel like I missed out a little bit. This will help a bunch with preparing for the GRE. Working through all the problem sets and watching these videos will be a rewarding and entertaining experience. I wouldn't say that he puts all my professors to shame, but he is definitely a remarkable professor.
ok to actually see that E through the verticals is indeed 0 one has to apply coulomb's law in cylindric coordinates, Ex and Ey will then vanish. still its kind of hard to grasp why E is really constant everywhere, i.e. also with a constant force on any test charge. well physics works but it can become sometimes very weird .
@25:48 I don't get it. How is it possible to determine the E-field of the infinitely large plane at location via a small closed cylindric surface? What about all the Q's still lying outside the cylinder and their contribution to E at location d ? Isn't it the purpose of the Gauss surface to have all those Qs within the surface like in the spheric example?
@mdinka E is 0 within a hollow, uniformly-charged sphere because the next field exerted by all the external charges cancel out. try this: draw a circle, choose a non-centered point within the sphere, and then draw all the contributing fields at that point. the addition of all the vectors should cancel out
Maxim, ya nye znayu cho takoye botanyk v vashom ponymaneye, no yesly etovo cvitochnika pritstavyt na minutky kak licom MIT, to ya uveren sho dazhe vu bu razkhakhatalys (udivilis). Da y vopsche, nyechevo obsuzhdat bolnykh ludey, seriozna. Vu shto nyekagda nye slushaly o ponyateye quotu? Ya svamy polnastyu soglasyen po povady sho amerikye nyechevo ponymat: koneshno, nabrala specialistov s CCCP i poryadok...
so, the magnetic fluz is equall to the product of the magnetic filed and the area the fiel passes through and the agnle between the fiel lines and the surface of the area they pass through,, measured in webers which is equal to one tesla per metre squared,
@Stratocaster1111 at 48:00? They had to be discharged before hand. If he had them outside of the sphere, it would push the positives out and the negative in (or vice versa depending on the sphere's charge). In the center there's no charge, because the forces would cancel each other out, so positives and negatives wouldn't get split up to each ball.
@digicho if you listen his words, he clearly says that the force of gravity WOULD BE ZERO at the center of a HYPOTHETICAL HOLLOW planet. he doesn't say that the earth's force of gravity is zero at its center. anyway, good on you for being that nobody annoying guy that needs to prove the expert wrong. congratulations.
@enki7777 Thank you, earthlings. Last time I have seen this the expert was saying differently. Not uncommon. Lately I ponder an idea of electrical pressure gravity where from spontaneously comes so called hollow earth. Let's say it's interactive.
@shturmanDark Да MIT собственно за свою науку известен, за исследования, за академиков. А учиться там на бакалавра это только бабло на ветер выбрасывать, если конечно нет гранта. Любой более-менее нормальный универ даст те же знания. Вот если же там докторскую делать - другой разговор. Там для этого все условия, тем и привлекателен.
@shturmanDark Ya bu tak nye skazal.... u menya collasalnaya uvazheneya k russkim universitetam y naukye. Nasha nauka #1, dazhe MIT mozhet paity pakurit bambuk! Y Amerikancu eto vsye prikrasno ponymayut, prosta pasmatry film "Iron Man 2" y vsye stanyt yasno kak dyen.
@62Chicago Извините, но вы обобщаете "дауны собрались" на основании одного человека который выглядит скорее как ботаник, а не даун, и сравниваете российскую науку и американскую на основании фильма iron man 2? Американцам ничего не нужно прекрасно понимать, у них наука финансируется, в отличии от России, или ваш опыт говорит об обратном?
@MaximPodolsky Maxim, a vu kadato sravnyvaly programu uchobu v russkykh universitetakh y angliskikh? Kstatye, v Rossiye shto nyelzya brat knigi damoj? - tolka za dengy??
@S1CKDRIFT3R He holds the chalk almost perpendicular to the board, but ever slightly away from the direction of motion (maybe about two degrees). Then, due to the high pressure, by moving the chalk he causes a skip-dragging effect where the chalk skips, lands and drags on the board very briefly, skips again, and so forth. Same principle as wet finger moving on wine glass rim causing a high frequency sound. Also same as the effect when you drag your finger on a steamed window with high pressure.
@S1CKDRIFT3R He holds the chalk almost perpendicular to the board, but ever slightly away from the direction of motion (maybe about two degrees). Then, due to the high pressure, by moving the chalk he causes a skip-dragging effect where the chalk skips, lands and drags on the board very briefly, skips again, and so forth. Same principle as wet finger moving on wine glass rim causing a high frequency sound. Also same as the effect when you drag your finger on a steamed window with high pressure.
@otTbc123 the magnitude of vector n-hat is 1, regardless of the area. The vector n-hat is there to indicate the orientation of that small area in space. If it's parallel to xy plane then n-hat is equal to z-hat (or k-hat in some books).
I still don't follow the superposition principle, especially the part when Mr. Lewin talked about the plates (infinitely large) and the E-field between is a constant. And that answer is given by the vectors going up and down. I don't understand why the vectors are always going down and doesn't cancel out between the plates
@YoAddicts because the plates have different charges and the vector always go from plus to minus, draw the picture and you'll understand, from the positive plate you'll have vectors pointing out of that plate and from the negative you'll have vectors poiting into that one.
@supersaiyan4vegeta20 in Russia there are only 10 grades and integrals are covered in the 10th grade. So I don't know what you guys in India do for 2 extra years. Seriously though, don't get a false sense of superiority because you think you "learned that in grade 12"
the r roof is just a unit vector. you would need the r roof for the potential because it's a vector, but you don't need it for the flux because it's a scalar quantity.
The balls were oppositely charged when placed inside the sphere. He then touched the balls together (without touching the sphere), which evenly distributed the charge difference between the balls. The point of the experiment was demonstrating that there is no field inside a conducting closed surface, while it is possible to create a dipole from the field from the external surface.
The balls would have remained charged had he not touched them together inside the sphere.
@md65000, the electric field is zero inside the sphere ONLY IF the charges on the sphere are distributed in an uniform way. But if you put a test charge inside the sphere, close to the wall, it will create attraction (or repulsion forces) on the charges of the wall, and therefore the charges in the sphere will not be uniform anymore and then the E inside due to the sphere is not zero neither.
The thing about the electric field being zero everywhere inside a (+)charged sphere is kind of hard to swallow. Then if you put a (-)charged particle anywhere inside the sphere it will experience no forces of attraction toward the wall of the sphere - even if you put it right up near the wall. If that's true then he's right - that IS an amazing result!
@md65000 I think you can easily understand it. If you put a charge, lets say the opposite charge of the sphere, then it will get attracted to the closest sphere charges since it is a strong attraction. BUT it will also get attracted to the charges at the other side of the sphere. Yes they are less strong but you have MANY MORE of them. So they cancel each other out.
@angello90pl Voltage is a result of the existence of the electric field. Mathematically it is the integral of E*dr = (kQ/r^2)*r = kQ/r [from coulombs law ]
The E you're talking about , I surmise, is the kinetic energy of a charged particle as it travels in the electric field from higher to lower potential by convention. Hence the delta V.
It's negative because a drop in pot en corresponds to the exact same increase in the kinetic energy and vice versa - analogous to an object in gravit field.
It means that if there was a positive electric field and a positive charge was placed in the field, then the charge's change in potential (delts V) will be negative because of the E-field's 1/(r^2) relationship. Delta V is dependent on E and E is dependent on Q, so Q is the only thing that "emits" anything.
im interested in a orbital system that could adjust a body's gravitational and fielding dynamic and to manipulate it in ways for human use and to make environments that wouldn't normally be usable, livable. Any one care to contribute to my madness?
If you pull chalk across a chalkboard at an angle it scratches off smoothly, but if you 'push' the chalk point-first across the chalkboard it bounces in your hand like he does. There are also annoying ways to make it make a screeching sound and have the class pulling their heir out for the aweful sound. ;-)
Wow, these MIT videos are great they put all my professors at the University of Michigan to shame. Why in the world cant all professors be like this???
i've watched all of these wonderful lectures and it's totally worth it. i'm already building basic motors, transformers & capacitors. now i'm re-taking this class & writing it all down in a text book.
If i understood the math, then perhaps it would be more understandable to me, but i do not.
If you have a sphere and it has no electrical force on the inside, then why does putting the opposing balls(dipole) inside eliminate the charge on the balls?
Same thing outside and far away from the sphere: no field=no dipoles when physically touching and electrons go back to rest. But close to and outside the charged metal shell dipoles are created when suddenly separated at that proximity since the sphere pulls electrons from the far sphere to the near sphere through its conductivity to induce the dipole effect.
At what age do Americans start college education? I'm curious because the topics covered in this module are taught in high school in some countries (where the Cambridge A level syllabus is followed). But we join college when we're 19 tho. I'm pretty sure however that noone else explains these topics as well as he does. Wish I had access to these lectures earlier...
I think the British system is 13 years of basic of education, while the American standard is 12 years. Correct me if I'm wrong, but I believe universities in the UK are three years compared to four years in the United States.
This is too complex. We got it all wrong when Voltaire supposed voltage increased with current flow ages ago when ideas were simplistic and technology crude. The guy made a mistake. The FMMC meter measures conductance = L/A (R=rL/A is wrong too). So when he increased his pile size we all fell for the theory that a fluid-flow increase was the result. Actually electrons became fewer but FASTER in the load wire. Think carefully about a meter in series with a variable resistor and you will find.
I have two strands of wire, and wind them parallel and untwisted on an iron core. Let's say the first strand is green and the second is red. In green wire, the current is flowing clockwise around the core. But, in red wire the current is flowing counter clockwise. Can I pick up a piece of steel with 2 amperes of current flowing through both pieces of wire?
How in the world, do magnetic assemblies, with odd numbers of magnets in opposition actually ever pick up more, than the same stack of magnets. What kind of scale issue is that, or is that identity?
I built the coil I mentioned a day ago. I have owned cow magnets, and made magnetic assemblies. What else can it be except seperate magnets, and about the same difference as the observer in the double slit experiment. Except that in that case there was the observer, and in this one, identity.
OK thanks i figured so. Its MIT , I don't understand why university is called college in the states. In Canada we have colleges and universities, where college is a step below university.
A University is a collection of colleges: for instance College of Arts & Sciences, College of Justice and Safety, College of Nursing, etc. If you attend a university, you are a college student. College is in no way "below" university.
For Gauß' Rule: h t t p : / / hyperphysics . phy-astr . gsu . edu/hbase/electric/gaulaw . h t m l (mind the gaps!)
partonace 2 days ago
around 22:28, why would the gravitational field of a cubical planet be 0?
4thKyuubi 2 days ago
@4thKyuubi i mean why would the gravitational field of a cubical planet WOULD NOT* be 0?
4thKyuubi 2 days ago
omg LOL i love his food pins... he wore an egg in the last lecture and a bagel in this one
wayly2000 6 days ago
Anyone else get 'Fitness Sexy Torture Workout" as a suggested video after this one?
kevineugenius 1 week ago
at 17:47 why is the electric field = 0?
4thKyuubi 2 weeks ago
@4thKyuubi
because Qinside = 0 (inside the chosen gauss surface), that's a key argument. If you don't understand that i would stop following.
slimmerikje 1 week ago in playlist MIT 8.02 Electricity & Magnetism
The normal force is dA?
4thKyuubi 2 weeks ago
@4thKyuubi
dA is a surface element, explained at the beginning of the lecture. the lenght of the vector dA is the magnitude of the surface element (explained at 02.02), this has nothinf to do with forces, don't know where you see forces.. look again please..
slimmerikje 1 week ago in playlist MIT 8.02 Electricity & Magnetism
@slimmerikje oh, he said that the book writes n*dA simply as dA. I assumed that n was the normal force? And dA is the surface area of that specific element right?
4thKyuubi 6 days ago
Best face at 46:55
Pdy18 1 month ago
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Pdy18 1 month ago
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Pdy18 1 month ago
The talking pink pixel is very clever
TheCrappyaccount 1 month ago
I wonder how many cats it takes to power Los Angeles
robertopercival 1 month ago
It would be nice if these videos weren't filmed with a calculator.
roastbeef240 1 month ago
@roastbeef240 can you seriously not read the equations or anything? it's not Avatar, it's a lecture.
ienjoyapples 2 weeks ago
It's great that the MIT provides those videos, but 240p? ;) haha
EinForster 1 month ago in playlist MIT 8.02 Electricity and Magnetism, Spring 2002
i wonder how he draws the dotted lines:S?
khanTatifur 2 months ago
@khanTatifur
with a piece of chalk which tip is dented
Omatunto 1 month ago
Best teacher. ever.
1PeaceNation 2 months ago
Wow, this course moves fast. In my physics class, we didn't get to Gauss's Law until at least a week or two after the third lecture of the semester.
stino22 2 months ago
mail2vpsinghh----I dont think anybody in the world can do this
elhanan1005 3 months ago
Damn, I'm glad someone in the class thought to use their calculator to film this!
ph7ryan 3 months ago
This has been flagged as spam show
I was curious to know that are these topics like gauss law, biot-savart law etc taught in college in USA?
I live in India and study in 10th grade and we will be studying that in 12th grade though i and many of my friends have already studied these topics....
shobhan126 3 months ago in playlist MIT 8.02 Electricity and Magnetism, Spring 2002
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shobhan126 3 months ago in playlist MIT 8.02 Electricity and Magnetism, Spring 2002
I am going to buy backboard and chalks and draw dotted lines all day
mail2vpsinghh 3 months ago
21:09 sounds like he made a mistake and corrected it afterwards
great teacher by the way :)
xenoepist 3 months ago
Which textbook do they use?
SpanosAngelos 3 months ago
no doubt you are the best teacher i have ever seen in my entire life.
hello12913 3 months ago
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sexoja23 3 months ago
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sexoja23 3 months ago
Dam this professor did so much in less than an hour and it made sense
have test tomorrow should have seen his videos earlier
deetoos 4 months ago
what happend if the professor don´t touch the plate??
otreborsolrac2 4 months ago
What bastard dislikes these
Superdoerr 6 months ago
@Superdoerr he applied pressure from one end of the chalk at an angle to board (greater than 90 degrees from the direction) and with the speed of his hand and the friction produced from the board, it makes it skip (learned that in art class :b)
silverag477 4 months ago
how did he draw that dotted line at 36:17 so quickly...?
molopo 6 months ago
@molopo the chalk skips across the board... sort of "chatters" or vibrates as it is pushed...
MichaelHGoebel 5 months ago
can scalers be smaller than 0? 6:47
TheFaceOfJohnPants 6 months ago
@TheFaceOfJohnPants
They can yes... Scalars and Real numbers are almost in all cases synonymous, they can take on positive, negative, and zero values
ilya150 6 months ago
@ilya150 thnx
TheFaceOfJohnPants 5 months ago
what is that little n^ means
1234dhawala 7 months ago
@1234dhawala it shows that n is a normal vector (has a length of 1)
correip 6 months ago
why is he always wearing his breakfast?
attilavirag 7 months ago 3
yes ye amazing conspiracy haha. Ive heard this topic 3 times n until now I didnt notice that every electric field at every point inside the sphere is equal to 0.
:O
Great teaching thank you shooooo mushh!!! :33333
JayantKumarZ 7 months ago
Is lecture 2 missing or is it just me?
Zebarbas 7 months ago
@Zebarbas Nevermind. It wasn't showing up when i searched it, but i played the playlist and found it.
Thank you MIT for providing this material for free, and thank you professor Walter Lewin for these excelent lectures.
Zebarbas 7 months ago
isn't this all taught in high school?
MultiRockzz 8 months ago
@MultiRockzz nah high school physics is basic this goes hard core.
deetoos 4 months ago
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julkiewicz 8 months ago
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julkiewicz 8 months ago
simply amazing.
11 people are dead in the water.
Kalec111 9 months ago
thanks for the vids one of the best finds on u tube!!!! prof Lewin is awesome!!
eeltruck 9 months ago
Great, I tested out of all my intro classes and I feel like I missed out a little bit. This will help a bunch with preparing for the GRE. Working through all the problem sets and watching these videos will be a rewarding and entertaining experience. I wouldn't say that he puts all my professors to shame, but he is definitely a remarkable professor.
3eshaw 10 months ago
this is what happens when one loves what he does
Incrue 10 months ago 38
I thought my professor was good but this guy is like HD television
Ralzaly 10 months ago 4
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Genesis113 11 months ago
Walter Lewin: Making other professors look like shit!
ATIhYdrax 11 months ago 56
@ATIhYdrax awesome comment!!! :D
gabinobarreda 5 months ago
Thanks Professor Lewin, I've been in bed all week with the flu but these videos help me keep on track with my classes.
yrsnkd 11 months ago 2
Half the time my prof doesn't even seem to know what he's talking about. Thank you Prof Lewin
funsize230 11 months ago 5
This has been flagged as spam show
PLEASE watch my video on the Electrinium battery.
electricitymagnetism 11 months ago
41:37
WoodrowTornado 11 months ago
thanks to this man i actually get this stuff now watched over 4 hrs of him thank u mit
dojOdRiFTeR 1 year ago
this professor actually wants us to learn !!!! AHHH SO BEAUTIFUL
karebear21 1 year ago
ivy league schools spoon feed theirstudents beyond belief not to mention most come from private schools
dojOdRiFTeR 1 year ago
@dojOdRiFTeR
If by 'spoon feed' you mean teach extremely well then yes you are right.
LegendLength 9 months ago 2
@LegendLength its the truth
dojOdRiFTeR 9 months ago
ok to actually see that E through the verticals is indeed 0 one has to apply coulomb's law in cylindric coordinates, Ex and Ey will then vanish. still its kind of hard to grasp why E is really constant everywhere, i.e. also with a constant force on any test charge. well physics works but it can become sometimes very weird .
mdinka 1 year ago
@25:48 I don't get it. How is it possible to determine the E-field of the infinitely large plane at location via a small closed cylindric surface? What about all the Q's still lying outside the cylinder and their contribution to E at location d ? Isn't it the purpose of the Gauss surface to have all those Qs within the surface like in the spheric example?
mdinka 1 year ago
Is the fact that the force F goes like 1/r^2 really the reason why E equals 0 within a hollow thin sphere ??
mdinka 1 year ago
@mdinka E is 0 within a hollow, uniformly-charged sphere because the next field exerted by all the external charges cancel out. try this: draw a circle, choose a non-centered point within the sphere, and then draw all the contributing fields at that point. the addition of all the vectors should cancel out
sixstring1991 1 year ago
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62Chicago 1 year ago
Maxim, ya nye znayu cho takoye botanyk v vashom ponymaneye, no yesly etovo cvitochnika pritstavyt na minutky kak licom MIT, to ya uveren sho dazhe vu bu razkhakhatalys (udivilis). Da y vopsche, nyechevo obsuzhdat bolnykh ludey, seriozna. Vu shto nyekagda nye slushaly o ponyateye quotu? Ya svamy polnastyu soglasyen po povady sho amerikye nyechevo ponymat: koneshno, nabrala specialistov s CCCP i poryadok...
62Chicago 1 year ago
so, the magnetic fluz is equall to the product of the magnetic filed and the area the fiel passes through and the agnle between the fiel lines and the surface of the area they pass through,, measured in webers which is equal to one tesla per metre squared,
junior1984able 1 year ago
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junior1984able 1 year ago
Why did he discharge the ping pong balls? Shouldn't he have charged them up before putting them into the hollow sphere?
The electroscope showed no charge because there wasn't any charge to begin with.
Stratocaster1111 1 year ago
@Stratocaster1111 at 48:00? They had to be discharged before hand. If he had them outside of the sphere, it would push the positives out and the negative in (or vice versa depending on the sphere's charge). In the center there's no charge, because the forces would cancel each other out, so positives and negatives wouldn't get split up to each ball.
MenialWitnesl1l 1 year ago
lol at 41:37 : focused.
bmx391xmb 1 year ago
@digicho if you listen his words, he clearly says that the force of gravity WOULD BE ZERO at the center of a HYPOTHETICAL HOLLOW planet. he doesn't say that the earth's force of gravity is zero at its center. anyway, good on you for being that nobody annoying guy that needs to prove the expert wrong. congratulations.
enki7777 1 year ago
@enki7777 Thank you, earthlings. Last time I have seen this the expert was saying differently. Not uncommon. Lately I ponder an idea of electrical pressure gravity where from spontaneously comes so called hollow earth. Let's say it's interactive.
digicho 1 year ago
Quick homework. How about propagation of charged infinite large cone?
BTW Doc's wrong about g inside planet which is not 0. Gauss is for surfaces.
digicho 1 year ago
@digicho If there's g at the centre of the planet, then in which direction is it pointing? "Gauss is for surfaces" what do you mean?
MaximPodolsky 1 year ago
Люди ..А ведь наши преподы ничем не хуже???? так почему наши университеты не столь привлекательны?
shturmanDark 1 year ago
@shturmanDark Да MIT собственно за свою науку известен, за исследования, за академиков. А учиться там на бакалавра это только бабло на ветер выбрасывать, если конечно нет гранта. Любой более-менее нормальный универ даст те же знания. Вот если же там докторскую делать - другой разговор. Там для этого все условия, тем и привлекателен.
MaximPodolsky 1 year ago 2
@MaximPodolsky Da tam vopsche kakiyeta downu sobralys na 41:37. Sho za khernya??
62Chicago 1 year ago
@shturmanDark Ya bu tak nye skazal.... u menya collasalnaya uvazheneya k russkim universitetam y naukye. Nasha nauka #1, dazhe MIT mozhet paity pakurit bambuk! Y Amerikancu eto vsye prikrasno ponymayut, prosta pasmatry film "Iron Man 2" y vsye stanyt yasno kak dyen.
62Chicago 1 year ago
@62Chicago Извините, но вы обобщаете "дауны собрались" на основании одного человека который выглядит скорее как ботаник, а не даун, и сравниваете российскую науку и американскую на основании фильма iron man 2? Американцам ничего не нужно прекрасно понимать, у них наука финансируется, в отличии от России, или ваш опыт говорит об обратном?
MaximPodolsky 1 year ago
@MaximPodolsky Maxim, a vu kadato sravnyvaly programu uchobu v russkykh universitetakh y angliskikh? Kstatye, v Rossiye shto nyelzya brat knigi damoj? - tolka za dengy??
62Chicago 1 year ago
This has been flagged as spam show
youtube.com/watch?v=LPwHxPIbZKo
Mein Exposee "Experiment Electrophorus"
Atomausstieg ist so machbar.
glanzi11 1 year ago
The professor teaching my e-mag course spends the entire time deriving equations. Very boring. >.> Thank god for this.
OddworldExodus 1 year ago
I wanna know how he makes them fast dotted lines
S1CKDRIFT3R 1 year ago
This has been flagged as spam show
@S1CKDRIFT3R He holds the chalk almost perpendicular to the board, but ever slightly away from the direction of motion (maybe about two degrees). Then, due to the high pressure, by moving the chalk he causes a skip-dragging effect where the chalk skips, lands and drags on the board very briefly, skips again, and so forth. Same principle as wet finger moving on wine glass rim causing a high frequency sound. Also same as the effect when you drag your finger on a steamed window with high pressure.
kossmikham 1 year ago
@S1CKDRIFT3R He holds the chalk almost perpendicular to the board, but ever slightly away from the direction of motion (maybe about two degrees). Then, due to the high pressure, by moving the chalk he causes a skip-dragging effect where the chalk skips, lands and drags on the board very briefly, skips again, and so forth. Same principle as wet finger moving on wine glass rim causing a high frequency sound. Also same as the effect when you drag your finger on a steamed window with high pressure.
kossmikham 1 year ago
estudiar en el tec de monterrey seria un gran desperdicio de dinero teniendo estos videos gracias MIT
thelastbattle19 1 year ago
thank you MIT and youtube and proffesor!
loxy777 1 year ago 2
Napoleon Dynamite makes an appearance at 41:37.
But anyways, I appreciate these videos and the teaching style of Professor Lewin.
Rasfuten 1 year ago
thank you Walter Lewin, thank you MIT, thank you Youtube, you are example of professors, schools and companies
huangcunbing 1 year ago
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jakeZaks2012 1 year ago
thanks internet , thanks youtube
trizniker 1 year ago
so electric flux is the amount of `electric force` that goes through an area,am i right?
In the formula: dɸ=E(vector) • ňdA, what has the surface of the area(dA) has to do with the magnitude of the vector which unit vector is n roof?
otTbc123 1 year ago
@otTbc123 the magnitude of vector n-hat is 1, regardless of the area. The vector n-hat is there to indicate the orientation of that small area in space. If it's parallel to xy plane then n-hat is equal to z-hat (or k-hat in some books).
MaximPodolsky 1 year ago
Another form of Gauss' Law: The Divergence of the Electric Field E is the Charge Density divided by the Electric Constant. ;)
OniLink10 1 year ago
Excuse me.
I still don't follow the superposition principle, especially the part when Mr. Lewin talked about the plates (infinitely large) and the E-field between is a constant. And that answer is given by the vectors going up and down. I don't understand why the vectors are always going down and doesn't cancel out between the plates
YoAddicts 1 year ago
@YoAddicts because the plates have different charges and the vector always go from plus to minus, draw the picture and you'll understand, from the positive plate you'll have vectors pointing out of that plate and from the negative you'll have vectors poiting into that one.
jalalmalo 1 year ago
India must be on top of shit then cause this is a 2nd semester calculus based college physics course
parrotdick 1 year ago 2
thank you alot for this.
1V10ntyPyth0n 1 year ago
yeah i agree..it matches perfectly with the 12th grade course in india..woohoo!
Thanks alot!! :)
PauliLop5 1 year ago
man, this is like 12th grade in india, is this the first year
supersaiyan4vegeta20 1 year ago
@supersaiyan4vegeta20 in Russia there are only 10 grades and integrals are covered in the 10th grade. So I don't know what you guys in India do for 2 extra years. Seriously though, don't get a false sense of superiority because you think you "learned that in grade 12"
MaximPodolsky 1 year ago 2
Perfectly matches with the Indian 12th grade course... thanks so much
joshkurien 1 year ago
At 10:13, I'd like to know where the "r roof" goes, my fundamentals in vectors are quite poor. I wonder if this has anything to do with that. Thanks.
Ananth22by7 1 year ago
the r roof went to see your mother
elyosbasha 1 year ago
the r roof is just a unit vector. you would need the r roof for the potential because it's a vector, but you don't need it for the flux because it's a scalar quantity.
weirdwei137 1 year ago
Can anyone recommend good supporting materials online (something that might have some of the info their textbook is supplying)?
keds93 1 year ago
guys,can somebody explain why did the balls loose their charge when he inserted them inside the sphere(the no electric field area) ?
shouldn't it just kept it's charge & never decrease nor increase ?
mst7eel 1 year ago
@mst7eel
The balls were oppositely charged when placed inside the sphere. He then touched the balls together (without touching the sphere), which evenly distributed the charge difference between the balls. The point of the experiment was demonstrating that there is no field inside a conducting closed surface, while it is possible to create a dipole from the field from the external surface.
The balls would have remained charged had he not touched them together inside the sphere.
CO2TROL 1 year ago
THANKS, much clear now
mst7eel 1 year ago
@md65000, the electric field is zero inside the sphere ONLY IF the charges on the sphere are distributed in an uniform way. But if you put a test charge inside the sphere, close to the wall, it will create attraction (or repulsion forces) on the charges of the wall, and therefore the charges in the sphere will not be uniform anymore and then the E inside due to the sphere is not zero neither.
rcalders 1 year ago
The thing about the electric field being zero everywhere inside a (+)charged sphere is kind of hard to swallow. Then if you put a (-)charged particle anywhere inside the sphere it will experience no forces of attraction toward the wall of the sphere - even if you put it right up near the wall. If that's true then he's right - that IS an amazing result!
md65000 2 years ago
@md65000 I think you can easily understand it. If you put a charge, lets say the opposite charge of the sphere, then it will get attracted to the closest sphere charges since it is a strong attraction. BUT it will also get attracted to the charges at the other side of the sphere. Yes they are less strong but you have MANY MORE of them. So they cancel each other out.
obaeyens 2 years ago
Last lecture he had a fried egg on his shirt, today he has a bagel. I guess tomorrow he'll be wearing an Egg McMuffin?
md65000 2 years ago
hey guys since E=-∇V, does this mean that negative Voltage would "emit" positive electric field, and positive V negative ef?
angello90pl 2 years ago
@angello90pl Voltage is a result of the existence of the electric field. Mathematically it is the integral of E*dr = (kQ/r^2)*r = kQ/r [from coulombs law ]
The E you're talking about , I surmise, is the kinetic energy of a charged particle as it travels in the electric field from higher to lower potential by convention. Hence the delta V.
It's negative because a drop in pot en corresponds to the exact same increase in the kinetic energy and vice versa - analogous to an object in gravit field.
jankokomuszek 1 year ago
It means that if there was a positive electric field and a positive charge was placed in the field, then the charge's change in potential (delts V) will be negative because of the E-field's 1/(r^2) relationship. Delta V is dependent on E and E is dependent on Q, so Q is the only thing that "emits" anything.
MRJerrod410 1 year ago
im interested in a orbital system that could adjust a body's gravitational and fielding dynamic and to manipulate it in ways for human use and to make environments that wouldn't normally be usable, livable. Any one care to contribute to my madness?
azezel2311 2 years ago
I wish he was my professor
sinuorette 2 years ago 3
i am seriously jealous of his handwriting
his lines and circles are so perfect and clean
Goatseeee 2 years ago
is this university stuff or college/cegep stuff in quebec?
erbol 2 years ago
how does he do the perfect dotted lines???
shim2dawg 2 years ago 3
If you pull chalk across a chalkboard at an angle it scratches off smoothly, but if you 'push' the chalk point-first across the chalkboard it bounces in your hand like he does. There are also annoying ways to make it make a screeching sound and have the class pulling their heir out for the aweful sound. ;-)
antoniorobateau 2 years ago 4
41:36 i love the "electromagnetic" hairdo
ellynx85 2 years ago 3
i should have been taking notes... i keep forgetting what all these variables mean haha
MikeHall683 2 years ago
Wow, these MIT videos are great they put all my professors at the University of Michigan to shame. Why in the world cant all professors be like this???
ride1157 2 years ago 57
@ride1157 UCLA too
rippertimmy3491 11 months ago
@ride1157 the difference between the two is their passion to teach or absence of in many proffesors nowadays
farestabs 11 months ago
@ride1157 My E&M professor at Michigan Technological University was right on par with Lewin. Dr. Robert Weidman is his name.
PlasmaOscillations 8 months ago
Professor Walter Lewin, the great.
tenzye 2 years ago 48
i've watched all of these wonderful lectures and it's totally worth it. i'm already building basic motors, transformers & capacitors. now i'm re-taking this class & writing it all down in a text book.
love this stuff! walter lewin is the win!
tolsonw 2 years ago 9
If i understood the math, then perhaps it would be more understandable to me, but i do not.
If you have a sphere and it has no electrical force on the inside, then why does putting the opposing balls(dipole) inside eliminate the charge on the balls?
xxjacobxx3 2 years ago
Same thing outside and far away from the sphere: no field=no dipoles when physically touching and electrons go back to rest. But close to and outside the charged metal shell dipoles are created when suddenly separated at that proximity since the sphere pulls electrons from the far sphere to the near sphere through its conductivity to induce the dipole effect.
;-)
antoniorobateau 2 years ago
people are already dropping out 1st lecture had 150k views :D
patrickramosmorano 2 years ago 11
superb no words to say,greeeeeeat
sanjivaniinamdar 2 years ago 2
excellent.. Love this.. I can at least take some classes that I have always been interested in.. thanks
wendlo1 2 years ago 2
At what age do Americans start college education? I'm curious because the topics covered in this module are taught in high school in some countries (where the Cambridge A level syllabus is followed). But we join college when we're 19 tho. I'm pretty sure however that noone else explains these topics as well as he does. Wish I had access to these lectures earlier...
Prearius 2 years ago
If they go into college right after high school then normally 18,19 years old.
xxjacobxx3 2 years ago
He eat on his shirt or what ?
It started with an egg, now a donut =))
Knowledge and fun, a rare equation. Often with two unkwown :)
Thanks for the vids, great serie
IceFritzLanger 2 years ago
I think the British system is 13 years of basic of education, while the American standard is 12 years. Correct me if I'm wrong, but I believe universities in the UK are three years compared to four years in the United States.
interxavierxxx 2 years ago
@interxavierxxx You are right
sonutulsiani 2 years ago
This is too complex. We got it all wrong when Voltaire supposed voltage increased with current flow ages ago when ideas were simplistic and technology crude. The guy made a mistake. The FMMC meter measures conductance = L/A (R=rL/A is wrong too). So when he increased his pile size we all fell for the theory that a fluid-flow increase was the result. Actually electrons became fewer but FASTER in the load wire. Think carefully about a meter in series with a variable resistor and you will find.
inertialcapacity 2 years ago
Who needs a physics lab with a teacher like this guy?
Mattprole 2 years ago
I agreed.
wackypro 2 years ago
superb.mind blowing no words 2 describe.prof lewin is my idol
dddiyamirza 2 years ago 4
walter lewin is the man... i haven't heard of anyone else who is able to put things that clear
giovanni9107 2 years ago 3
I wish I could pay him a visit... Is he still teaching at MIT?..
yanarabelllin 2 years ago 3
I'm taking this course in the Fall. How great to be living in a time where a Ivy League lecture is offered so conveniently. Praise be to God.
Kingarthur305 2 years ago 3
GGGGGRRRREEEEAAAATTTT and nothing else
umayrpkhassan 2 years ago 6
oops i made a mistake in my work he must be right no mistake, but that was not the reasomn why inside was 0
goodluckpeace44 2 years ago
wtf 4.05??/ lol
madgaff 2 years ago
malheureusement nos cours ne ressemblent pas à ça ^^
Leider sehen nicht unser Unterrichten so aus !
jeannotlapin33 2 years ago
I have two strands of wire, and wind them parallel and untwisted on an iron core. Let's say the first strand is green and the second is red. In green wire, the current is flowing clockwise around the core. But, in red wire the current is flowing counter clockwise. Can I pick up a piece of steel with 2 amperes of current flowing through both pieces of wire?
What if I say, yes.
FlavoredCoffeeGuy 2 years ago
How in the world, do magnetic assemblies, with odd numbers of magnets in opposition actually ever pick up more, than the same stack of magnets. What kind of scale issue is that, or is that identity?
FlavoredCoffeeGuy 2 years ago
I built the coil I mentioned a day ago. I have owned cow magnets, and made magnetic assemblies. What else can it be except seperate magnets, and about the same difference as the observer in the double slit experiment. Except that in that case there was the observer, and in this one, identity.
FlavoredCoffeeGuy 2 years ago
lol 13:20
OCD much? I love this guy
hausfeldt 2 years ago 2
he saves my butt in AP physics...
and that is a bagel on his shirt right???? what?
itsarandomlife 2 years ago 5
what's with the food he puts on his shirt? (fried egg, donnut...)
andresordo 2 years ago 4
lmao i know, they say geniuses are often exccentric i guess he's a case in point =)
mremile72 2 years ago 3
beautiful mind
nangbutinang 2 years ago 3
yeah, this guy knows eactly what he is going to say, and how he is going to present it. It's not some guy winging it, that's for sure.
Baker5874 2 years ago
i learn more from these online lectures than attending my own physics lecture. thats what you get with MIT i guess
sthaznpride17 3 years ago 3
prof rocks!
lianghaochen 3 years ago 7
OK thanks i figured so. Its MIT , I don't understand why university is called college in the states. In Canada we have colleges and universities, where college is a step below university.
oshawaphysics 3 years ago 3
A University is a collection of colleges: for instance College of Arts & Sciences, College of Justice and Safety, College of Nursing, etc. If you attend a university, you are a college student. College is in no way "below" university.
needmicrophone 3 years ago 4
Is this first year physics, anyone know?
oshawaphysics 3 years ago
yea this is second semester of college physics.
gottalovesci 3 years ago
calculus-based college physics
teejay1618 2 years ago
Gauss's Law- 11:47. YES.
hellosummy 3 years ago