8.02x - Lect 6 - High-voltage Breakdown, Lightning, Sparks, St-Elmo's Fire
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- Опубликовано: 29 сен 2024
- High-Voltage Breakdown, Lightning, Lightning Rods,
Sparks - Hindenburg Disaster, Static Charge Induced Gunshot in Lectures, Great Demos
Assignments Lecture 6, 7 and 8: freepdfhosting....
Solutions Lecture 6, 7 and 8: freepdfhosting....
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!
Walter Lewin is the best teacher i have ever had ......
Truly magnificent, Sir you really make me love Physics...
Lectures by Walter Lewin. They will make you ♥ Physics. do u rthink benjamin fraklin did experiment of kite as it was high voltage. he might be died on the spot
why do you keep touching the metal plate to witness the shock
your lectures made me love physics ❤.. " finally in your orbit mr. lewin"
Walter: THANK YOU! I really appreciate your work, and I know it's not easy to make these things accessible like you do.
That girl at 20:38-20:41 seems absolutely ecstatic!
Perhaps she is taking in the knowledge via acoustically. Where is she in life now?
why does my man have a banana as a pin-up on his shirt?
The idea is used in scifi-movie the inter-stelar I think when then machine gun has a small lighthing, go back to the problem where puller is stucked often when collected heat. (I think as it is in movie and my imagination then I can tell).
@ 13:39 ...I got confused... i couldn't understand how they are setting electric field to 3 million v/m by making "d" 0.1mm... since for an infinitely charged sheet, electric field doesn't depend on distance...
So the misunderstanding is.. We dont make the electric field 3 million by making the distance 0.1mm...It's the other way around... Since the electric field is set to 3 million.. the voltage will be 300 volts only at distance 0.1mm ... and as we took the voltage as our given.. we are reverse engineering to find out what the distance would be
"END IT WITH A BANG", quite literally 😂😂
33:53, today it's called COVID-19 discharge
52:06 "a small bloop, and since it's going to be very small, at best..." he said. "You have to be very quiet, otherwise you won't hear anything," they said.
+Onesockanda Song That was no bloop. I was drawing sparks from the Van de Graaff usig a share point and if students are very quiet they can hear the cracking noise of the sparks,
+Lectures by Walter Lewin. They will make you ♥ Physics. lol are you actually Walter Lewin? And I was referencing another part of the video
+Onesockanda Song Yes I am Walter Lewin. I run this channel.
+Lectures by Walter Lewin. They will make you ♥ Physics. Well it's an honor to talk with you, then
@@lecturesbywalterlewin.they9259 love you sir (from India) . I'm 16 and I've seen 8.02 and loved this😊😊
I have to say this!
Walter Lewin is the best teacher, i've ever had. Literally makes you love Physics.
Isn't every teacher is supposed to have this quality (of making you love his subject)!
He is a true inspiration..
+Rainman 10 Thanks Rainman for your kind words.
thank you for Posting this! I have a better understanding of Lightning and coronal discharge now :) I have indeed seen St Elmo's fire on a metal fence post near my maple tree. Luckily the tree is unharmed as it occurs often before a bad thunderstorm. But I also live under high voltage power lines and have no lightning rod on my house.
Why does Walter Lewin have to touch the metal plate before touching the metal plate to the pan? Doesn't touching the plate get rid of the charge? Doesn't he want the charge to stay on the plate, so that it can then charge the pan? What am I missing?
@@raymondblake5765 I also can't figure it out..
@@raymondblake5765 I think he wanted to know if there was still charge on there, if not then he would continue rubbing the cat fur ?
Sir Walter Lewin is the spark that illuminates us the path to love physics.
Thanks to you i really love physics.
He is very good
My physics teacher just reads a powerpoint and lets students use Chegg during exams. DURING EXAMS. Which indicates, to me, that he only cares about his image of being a good teacher as he passes students along who will make terrifyingly inaccurate engineering solutions to real-world problems.
These videos are gold to me.
33:52 That's where I heard the term Corona first
yes bro but this corona is related to sun and light ; not to disease .
At the end...OMG moment 😂
😱😱😱😱😱😱😱😱😱😱🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯🤩🤩🤩🤩🤩🤩🤩🌟🌟🌟🌟🤣🤣🤣🤣🤣🤣🤣🤣🤣
Thank you for making these fantastic lectures available, I´m a little late to the party attending college in my thirties and the demonstrations are so much fun that my kids like watching them with me.
+Hallgrímur Steinsson It's NEVER too late to start loving Physics, and being in your thirties is an excellent age to start!
30 years old now. 8 years late to the party, though. 😂
@@CurrentlyObsessively Yeah 😂
Am i early in this party because i am only 17😂
Being hit by a spark and hearing this tremendous shot without ear protection?
Bless you, Mr. Lewin, for I'm afraid it wasn't your lucky day!
Much love from Brazil! :)
what the hell man only 32 k views on such Quality video and 2M views on that 1000° knife idiotic videos. ..... why people are not taking advantage of technology Mann it really hurts
Because people are stupid and they don't care anything that doesn't affect them. But only people who can see potential for ex. scientists and some engineers are excited and they do really care theese things...
Rohit the USA is filled with liberal college graduates who are more interested in brain dead idiots, instead of something that is really educational. And they don't have the intelligence to understand what he is saying. Other words they are STUPID.
views number is not a criterion even for songs stupid song like decpacito has billions while other classical high level of lyrics music less than a milion
because 9 year olds aren't going to be watching college physics lectures???
His teaching will definitely clear our fundamentals..d ways he shows experimentally...its awesome....will greatly help in my jee prep
The lecture was amazing!!!! i was sitting on the edge of my chair, enjoying the lecture thoroughly, about sparks and lightning! Thank you for so much of "phun with physics".
:)
What a practical approach of learning, absolutely very interesting lecture..I am working as a physics teacher and I am learning from professor how to teach the students...
One of my hero’s. Shame I’m a chemist 🤣 but I absolutely love your lectures...thank you for sharing.
52:40 Well let's see whether we can use this instrument. 🤣🤣
During my studies, I have never seen such a great explanation of a subject as from professor Lewin. When I consider the fact that he even finds free time to explain additional questions in the comments after all these years, I am truly shocked. As I don’t like youtube (and other social networks) in general because of the commercial, boring and useless staff, I really appreciate that this time youtube and prof. Lewin can hand over their knowledge so we can make a world a little bit better. Thank you
When electrophoresis why is he toching with his hand after car fur rub pls. Anyone explain...???
He says:
"Corona Discharges"
Everyone after 2021:
~~STRONG FLASHBACKS~~
Great lecture, concept of electric potential really coming together very well now. Thanks, professor and happy recent birthday!
2021 anyone?
I admire you, professor Lewin. You are a great inspiration for me :)
The end is very surprising! I enjoy the lecture a lot. Thank you, prof!
Glad you liked it!
is there Nobel prize for teaching?
Sadly no.
You are so good as my physics teacher. I love ur work and your practical skills. So happy to have your lectures....
9:49 this is one of the coolest things I’ve seen so far
:)
Lectures by Walter Lewin. They will make you ♥ Physics. I can’t believe you responded😁 I’m loving your lectures. One day when I am a grad student I will try to make my own lectures as interesting as yours are. You are a huge inspiration!!
Thank you very much for sharing your knowledge with everyone.
Sorry ... It is necessary to put your finger on the electrophorus each time?
If anyone has problem 2.7 please comment it or show me the link to it. I can’t find it! Thanks!
the moment i saw the banana i started uncontrollably laughing,don't know why!
the same happened with lecture 2(the egg!)
is that a way to grab students' attention?
Not Really.
So, why those "fruits" are there for ?
Wireless mike battery pack cover.
hello sir i am curious why are you wearing a banana
7:33 we know that the glass is positively charge. So when he touches the glass with pan, some charges are transferred to the pan. And when he touches it won't the electrons from ground come neutralise it?
The glass is an insulator, so little to no charge will be transferred between the glass and the metal pan. Instead, there will be induction, electrons from the pan will get to the bottom closer to the glass, leaving positive charges behind on top. When you touch the pan, electrons come from the ground to the metal pan because they are attracted by the positive charge that the pan has due to the induction. In that way, the pan was negatively charged through induction.
A more common type of electrophorus is that instead of using glass, styrofoam or other material that has more tendency to get negatively charged through rubbing is used. In that way the styrofoam plate would get negative, making electrons on the pan to go on top away from the styrofoam due to repulsion, leaving protons closer to the styrofoam. In that way, if you touch the pan you remove the electrons from the pan and they go from your finger to the ground, making the pan positively charged through induction.
I find this type of electrophorus method more intuitive than the other method. Actually if you look on the internet for electrophorus charging, you probably won't find someone explaining the case where there is a glass plate (or another plate) that has more tendency to get positively charged through rubbing.
Thank you Walter Levin, you are a great teacher!
:)
Best teacher ever !
Why has the professor attached banana to his pocket?
Please tell me
when.you scuff your feet on a carpet, you gain electrons and become negatively charged. If you then place your finger near a metallic surface, such as doorknob, an electric field develops between your finger and the doorknob. As your finger gets closer to the surface, the magnitude of the electric field increases. when it exceeds a threshopd of 3MV/m, the air breaks down,creating a small lightning strike, which you feel as a shock.Estimate the distance between your finger and a doorknob at the point you feel the shock.
Sir I love physics but I don't like mathematics much. so is it necessary to be a mathematician first to love physics or to explore physics ? what should I do please tell me sir?
Hi Professor Walter, I'm a mechanical engineer student from Italy!
My physics professor during one of his lectures gave us the exact same demonstration about the different distribution of charges on smaller radius corners. He eventually told us at the end of the lecture, that the demonstration is fundamentally incorrect, and that there is a profound CONCEPTUAL ASSUMPTION (no wrong calculus) we made that is profoundly false.. but he then said that, despite that wrong assumption, that model works pretty well at explaining why that happens.
He then gave us the task to find the wrong assumption we (and you) made... what would you say about that sir?
sir you are simply a legend ..
no classes of this generation can beat your style of teaching
This explains why MIT is one of the finest Engineering School in the world because of high caliber and finest professors and only top students are accepted.
The part I don't quite understand is, in eg. Denmark this (most of it) is taught in the advanced physics course in high school already. Not full electromagnetism, but electrostatics.
@@skuula electrostatics is taught in high school everywhere, electricity and magnetism is where the true difficulty lies which he didn't really get into in this vid
@@skuula Yeah I was also surprised that this was taught in an engineering class. This is very basic stuff.
20:38 WOW
Lightning discharge some kind of "step leader" discharge propagation phenomena is very very hard~. this is because of the multiphysics, maybe coupled with fluid, thermodynamically with electromagntics~. even simple problem only in the electrostatic case, the space charge problem makes you tired, or self field current->lorentz force
3:28 sir when Q is directly proportional to sigma then how sigma b = sigma a /5
I watched at 3:28 and I cannot add to the clarity. I suggest you watch it again and pay more attention.
Researching the effects of imploding high voltage fields.
Thanks for clarifying charge area vs. Charge density. (I always wondered about that.)
:) Happy Happy
Sir why does current last only for a short period during sparks.
Congratulations Sir on one million subscribers 😍😍😍
Professor Lewin is an absolutely inspirational educator :) I'm currently working a public science communication job, and hope to return to school and become a professor myself; These lectures are giving me loads of demonstration ideas, extraordinary perspectives on explanations, and best of all, I'm learning so many things I didn't know before. Thank you sir!
Teaching is really really hard task. It is a journey, and Professor Walter Lewin has shown us the true way to learn Physics. Thank you Professor for your lectures. It has been the most helpful.
13:30 sir if we had such perfect plates then from which point exactly would the spark happen since the E field and charge are same everywhere
i want to ask two questions please.
the first question, from where the electron in 9:06 comes from?
the second question what will make the ions neutralized again 10:00? in other wards, how the ions will be neutralized again?
sir , how had you considered
the potential as 10 V at 11:23 min..
watch again and listen again.
I explain it well.
4:12 Here,Strength of E near the surface of conductor equals strength of E between two uniformly charge distributed infinite plane i.e E=σ/ε0.Clearly equation make sense
but why they are same?
I did not understand how come current is being drawn from the Van de Graff to the ground through that sharp object without generating any visible effects ? Is it the displacement current , treating the air as matter with non zero susceptibility ? What is happening in between the sharp tip and the Van de Graff ? Will I get shock of I put my finger in between ? Kindly drain away this question from my mind by correcting me if I am wrong. Pardon my brevity Walter Lewin Sir ! Take my love Sir. I have learnt a lot from your lectures.
can anyone tell me the significance of his batch stick to the shirts he wears in his every lecture?
Live long pray for u sir. Excellent donation of knowldge for students from u. I appriciate u sir.
:)
Sir I am from India...I am a medical student now I like physics very much..I do not have even maths coz of education system... Pls guide me
Why does the air not Ionize during this charge from the Van de graaff machine and the pointed conductor, i.e. why was there no spark between the machine and the pointed conductor like there was with the metal sphere. Does the arc/spark only occur between non sharp objects, and if so why; I thought it had to do with the air ionizing and becoming a better conductor so why wouldn't that happen between sharp objects as well? Is it that the rod is too far away for all of the air in-between to be Ionized or is it something else entirely? If it is just the distance, would eventually over long periods of time, the column of ionized air grow the bridge the gap between the two objects and create an arc?
i am taking the same course at my university, thank u very much for making this accessible to anyone... the lectures in my university are so boring and the doctor who teaches us only reads from his papers soo I am studying this course using ur playlist even though I study in a different language
thank the universe that u exist
two questions that interest me are when were these lectures captured ? and until lect 6 were learning the same subjects so the rest of the lectures in this playlist are still relevant right ?!
2002 - try MIT's 8.022; it's more advanced - it's on MIT OCW and on edX
@@lecturesbywalterlewin.they9259 thanks professor, I checked them out and yeah they look more similar to my course because I am studying electrical engineering , but still the lectures here helps me build an intuitive thoughts on problems and concepts so I think I will still watch them to build a good basis for the advanced material in my course. thanks for replying so quickly I really appreciate ur help
A life devoted to teaching physics.
Holy crap that loud bang scared the life out of me small pop more like a sound out of a firework holy moly shut the front door it went of at the same as I wrote this comment😱😱😱😱😱😱😱😱😱😱😱
I can't have enought of your classes Mr Lewin! (So, I bought your book :-) ) Thank you for sharing your lectures on internet, that way you continously are becoming a teacher for everyone who want to be your student, you are very generous!
:)
Dr walter lewin
l hope that you read my comment l really love your way in physics you made me a scientist in physics , nowl have my frist PHD in physics.
If proton move can current is produced
we would not call the movement of 1 charge a "current" but that's a matter of semantics.
What comprises of the return stroke? Are these the electrons travelling from cloud to earth. If yes then why it is called the return stroke, its isn't travelling in the opposite direction. Please tell.
I wish I had professors like this when I was getting my EE and physics degrees. In the past, professors excelled at teaching their subjects by explaining them in intuitive ways, showing demonstrations and, most importantly, they taught their students HOW to learn. These men and women are what made our country strong in technological fields.
:)
But for the pointed surface, from where do we consider the radius? What can be a more generalised mathematical proof?
You made me love physics. Thank you so much sir.
small bloop I was expecting for a sound more like the burning of hydrogen
why when they become neutral they make light? i thought was due to accelerating charges producing light is why
Why does Walter Lewin have to put his finger on the metal plate before using it to charge up the metal pan? Wouldn't putting his finger on the plate get rid of the charge on the plate?
39:50 corona 😒
If the two sphere are connected by conducting wire...how the potential are same
Yes, they are getting good value for their $27,000 tuition.
In other words, you crimp a wire and at that crimp spot it will heat up more and eventually it will burn.
I really hope that you reply to my previous question. Even if you say impossible.
Thkx sir for such amazing videos and practicals :D :D physics
Sir in 17:34 if there is electric field on the surface , then like inside the conductors why doesn't the charge on the surface move and kill the electric field on the surface.
the dome of the vdG is a conductor. E-field inside the dome is zero. E field on the surface is Q. This is static charge which cannot go anywhere unless you drain it off (e.g., by touchng it).
@@lecturesbywalterlewin.they9259 Thankyou sir, sir but why doesn't the charge on the surface move due to the electric field on surface.
@@anandapatmanabhansu no charge can move due to its own E-field. The E-field is radially outwards does each charge creates locally that E-field. If you have 2 charges separated by some distance they each will start to move in the E-field created by the other charge.
@@lecturesbywalterlewin.they9259 Thankyou sir, but why does charge move inside move and kill electric field inside
its alomost 2023 and this lecture still gives me hope that we wont get malaria.
How did this guy suck me in so deeply and suddenly I now have have a wealth of understanding of why lightning hits the points of an object instead of the flatter portions?? Regardless of the complexities I had to restore in my brain, he runs through the logic PERFECTLY!! This guy is a GREAT teacher!!! 👍🏻😎👍🏻
52:05 yet another reason why I love science!
Thankyou so much sir love from india♥🇮🇳
They've got rifles in a lecture hall.. Could it be any way better??😂😂
Who created that marsh gas at lobby 7
Why are you touching with your finger during electrophorous process?
so you can determine the smoothness of a sphere by calculating how much charge the sphere will accommodate
not directly, but yes
Corona is discharging our lifes. Is it Professor lewin the resaon? lol
Professor Lewin, hope you're doing well! You mentioned here a memory when you were an ungraduate, what was your major if you don't mind me asking?
Physics major as undergraduate
According to WikiPedia, air can begin to break down by an electric field of about 3 x 106 V/m, but I have no idea why can't E exceed 3MV/m here 17:40 . Can anybody explain why?
Sir I have a question. A cylindrical capacitor charged with +Q on the inner conductor and -Q on the outer conductor has, according to the book and your P.1.b) E = Q/(2πεLr). This is the field for a Gauss surface encolsing the inner cylinder with +Q charge. However, the outer (hollow) cylindrical conductor has a charge -Q on its inner surface (its very thin but still the conductor has E=0 everywhere inside apart from the surface facing inside). If I take a hollow cylindrical Gauss surface with the outer surface inside the outer cylinder (E=0) and the inner surface in the space in between the two conductors shouldn't I have one more contribution to the Electric field due to the enclosed -Q in this gauss surface? Is the surface I took valid?
The resulting field will be the same but without the factor of 2 in the denominator.
Sir , I am a student from India. I viewed all your lectures. It was a visual treat for me. Thanks for everything. I wish to do the assignments of 8.01 and 8.02. In 8.02 assignments you have written reading from Giancoli. Sir, can you please tell the exact name of the textbook and which edition it is? Because then i can track the pages and problem nos. as specified in your assignments? Again, for 8.01, you have specified reading from Ohanian. What is the name of the text book and the edition of Ohanian? Sir, please reply. It would be a great help if you can tell me exact name and edition of these text books? For 8.03 assignments, you have specified the full name of text books (A P French and Bekefi & Barrett (ISBN No. etc). Like that can you tell me details of the text book for 8.01 and 8.02. Thanks a lot for the lectures Prof. Lewin Sir. Take care Sir. Lots of love from India.
why potential in A is equal to potential at B.(conductor in equipotential means
Because they are conductors, the charges will move such that they experience no electrostatic forces, therefore making E=0. So Potential is the same.
12:00 I think it should be mean(E) = - ∆V/∆x because E⃗ = - grad(V) , if I'm right, I have to say that it is incredible how few mistakes you make… If I was in your position I would have done a lot more, thanks for these amazing lectures
What an amazing lecture. Thank you.
5:07 Sir i think I'm confused at this part .please clarify my doubt sir...How on Earth is that possible to do the same work in bringing one coulomb of charge from infinity to a sharp edge and a surface with low charge density of a conductor when they have different magnitudes of electric field on both the sides?🤔 Isn't that a violation of conservation of energy? (Or) Are they implying the electric field only at the point of that surface...and electric field will not be a constant value as the distance increases.. the electric field from the surface with small radius of curvature will go down very fast when compared to that of the surface with small charge density so that both the workdones will be same when I reach the surface from either side by bringing one coulomb of charge in my pocket?🤔