8.02x - Lect 4 - Electrostatic Potential, Electric Energy, Equipotential Surfaces

Electrostatic Potential, Electric Energy, eV, Conservative Field, Equipotential Surfaces, Great (& dangerous) Demos!
Assignments Lecture 1, 2, 3, 4 and 5: freepdfhosting.com/2cb4aad955.pdf
Solutions Lecture 1, 2, 3, 4 and 5: freepdfhosting.com/75b96693f2.pdf

[@lecturesbywalterlewin.they9259]

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!

[@rahultiwari9003]

Sir are you the real Walter Lewin ???

[@RealSmiller]

I don't think so

[@1GENKILL4]

+Rahul Tiwari I've always thought it was him.

[@Stonehappy420]

Matt, Rahul, Real, Walter Lewin makes a great effort and actually takes pride in answering as many if not all of his students questions, in class or not. If it is in regards to the lecture, ask away friend... and if not here, you can always find more content on MIT OpenCourseWare (ocw.mit.edu). This is from my experience at-least, it has been a little while since I have asked a question, I am unable to read the Future, but he is a good man, have faith.

[@vaishnavkumars9261]

this comment will make him happy , it makes me to !! thanks @Lerrad Noillik

[@siresquire9439]

I`m a simple man who's still in awe at the dotted line skill. Drrrrrrr :-)

[@bernasantosdias]

Professor Lewin, thank you so much for making these lessons available to everyone. You have inspired millions and definitely changed the way how many people see physics. As an undergrad student, I find these lessons an excellent supplement to my normal classes. You are a legend. Best regards from Portugal!

[@lecturesbywalterlewin.they9259]

:)

[@HarshYadav-np4bn]

@@lecturesbywalterlewin.they9259 You are a great teacher love from India 🇮🇳🇮🇳🇮🇳🇮🇳❤️❤️👏👏

[@malvikaawasthi2457]

@@lecturesbywalterlewin.they9259 you are a wonderful teacher as well as a person

[@attamuhammad7344]

Love you very much from Pakistan 🇵🇰🇵🇰🇵🇰🇵🇰

[@ManjunathManju-dv9df]

@Lectures by walter lewin sir

[@ipshie]

What a legend. He still replies to many comments even after so many years since the video was posted

[@anuragbind3159]

Yes he is awesome we Indian too need like this teacher's btw this year world best teacher award winner was Indian!

[@lisaa23581]

@@anuragbind3159 indian gang here🖐️

[@dyutibiswaspotterhead5268]

and another thing did u notice? most of the people seeing his lectures are Indians and most probably IIT aspirants :)

[@dipayanchowdhury5990]

Sir, the way you teach is just amazing. My Physics teacher just used to come and do some derivations and solve a bunch of questions. BORING! But you make Physics fun! The way it should be! Thanks a bunch! You are a saviour! :D

[@lecturesbywalterlewin.they9259]

:)

[@cagataysunal1130]

"My Physics teacher just used to come and do some derivations and solve a bunch of questions. " same.

[@oguzkaanylmaz1838]

My teacher wouldn't even bother with derivations. Would just give us the formula and expect us to apply it. School really isn't a place to learn.(high school)

[@sarthak8350]

Mine also , derivation - numerical - repeat I hate attending my school teacher's lecture 😌

[@pubgplayer1720]

@@oguzkaanylmaz1838 Learning physics through formulae is by far the worst way to do physics. Easily.

[@marlon123444]

Sir Lewin, I admire your whole discussion and presentation, I'll promote this video to my classmates promise, Thank you!

[@lecturesbywalterlewin.they9259]

+marlon123444 Superrrrr, Thanks!

[@PhoenixX6T4]

@@lecturesbywalterlewin.they9259 same sir I also promote your lecture to my classmate

[@CraigHollabaugh]

Professor Lewin, I've been learning about vacuum tubes by reading 1940s textbooks, Spangenberg's Vacuum Tubes in particular. Your 8.02 lectures are an excellent companion for my research. Thank you for clearing explaining physics at this level, a true treasure.

[@supriyoain2700]

Professor Lewin is soo friendly to students, and such a godly teacher. Just listening to his lectures brings a smile on my face! Good thing I was born in this era!

[@vishnu-ph9sm]

11:13 why nobody is talking about his perfect circle...!!

[@ashishjoshi8628]

Because you are talking

[@beingultimatelikeapro7402]

Because its ellipse😂

[@adokapo]

This man got energy of an young boy ;) He is gonna live long life!

[@radheshyamvarshneya4113]

He is one of the best teacher on Physics I have come across. His demonstration, practicals and the wit are unique. Not many teachers are so well clear about the subject. His website is a great asset to millions of students across the world.

[@dr.aliahmedsabir5192]

prof lewin i am from india ,Bihar my brother who is IITIAN appreciated you alot! he always talk about you! you r great

[@lecturesbywalterlewin.they9259]

:)

[@cankayabek949]

Back in 2009 or 2010 (from MIT website) these videos made me get a very high score in exams and especially the experiment part of this video is the part i remember most accurate :D You are absolutely the best at teaching the concepts, I cant express how thankful I am.

[@muhammadahmadarshad5658]

Thanks, Professor Lewis for taking electric short for us.

[@dy8576]

there is something satisfying in seeing practical demonstrations of concepts you have just learnt. The friction inside your head gets reduced.

[@plugbitsproducts5462]

If I was there in your class every time at the end of your lecture I was clapping and absolutely happy to give you the feeling that I get from your lectures you are an amazing person and amazing teacher Thank you very much for all!

[@priyabratadash381]

Fantastic lecture, incredible. The real beauty of this kind of lecture is that, the concepts directly goes into the head of student and the most important thing it conveys is that " physics is written in text books but exists in nature " Thank you Professor Walter Lewin 🙏 Love from India 🇮🇳🇮🇳🇮🇳🇮🇳

[@fredsilvers1427]

He is such a good teacher that I am able to follow along with some understanding that keeps building as he goes. Yet I don't know calculus and not much trigonometry. Now I am driven to learn both of those forms of mathematics in order to follow him through his equations as well and have the ability to apply them in any scenario. I wish I could go to college.

[@Phuongimp]

Oh my hero. I wish you all the best wishes to you and your family. I love the nature and physics behind it by your inspirational lectures.

[@mukeshraj.s7325]

I am an Indian,i am studying High school class12,and i am watching 5his lecture for my exam tomorrow.Thanks a lot sir.

[@royvelazquez3061]

Excelent!! Walter Lewin, you safe my life! Greetings from Capilla del Monte - Paraguay

[@lecturesbywalterlewin.they9259]

+Roy Velazquez If I saved your life, you owe me one! ha ha ha

[@priti9629]

@@lecturesbywalterlewin.they9259 we all owe you sir

[@Hardik_choudhary924]

thanks, sir. you make everything more interesting by doing all those experiments

[@priti9629]

you are THE BEST PHYSICS TEACHER who could seriously make us watch through the formula and we realize physics is to love not too just pass some sort of Examination

[@Renthlei_Jr]

0:30 Electric Potential due to point charge 12:00 electric potential at any point in space

[@warmpankake962]

This was very helpful, thanks

[@arpitsharma8947]

these lectures should be upscaled and put on KZbin, these are treasure troves

[@NovaWarrior77]

This guy is the perfect blender of theoretical and experimental physics!

[@DaysChallenge-fx8xc]

Sir i just wanna say thanks as you r helping millions of students to get to their dreams. I m an IIT aspirant and I can Confidently say that no one can demonstrate physics in such a way u can.... Thanks a lot sir😊😊

[@dank501]

Thank you for this! Phenomenal way of displaying the math and how it ties into the concept!

[@PymGordonArthur]

Thank God for this man and this administratation that allowed this to be publicly available.

[@kingk6995]

You are really making physics feel to us. Thankyou professor.

[@APmotivation3290q]

This type of education should be given in every college of India... but just learning learning... memorizing all the things and no practical experience no real life analysis 😪😪😪😪 just giving importance to how broadly you have answered. Sir 🙏🏻🙏🏻🙏🏻great.

[@deokaransingh7943]

Amazing just amazing. World needs more tutors like u sir. It's the style of teacher which makes a subject interesting or boring. Thnx a lot sir for inspiring us . Love from India ! 🙏🏾🙏🏾🙏🏾🙏🏾🙏🏾

[@narayaniwategaonkar]

Thank you professor for making these incredible lecture available for us❤️🙏

[@aimxnvn_x_geness4998]

Really helpful in my undergrad medical preparations here in India. Thank you sir.

[@aaminalone9008]

Sir Lewin you are a great teacher. You are the person who makes us to feel the beauty of physics. Thanks for your lectures...

[@jimba6486]

I was so lost on what was going on in this chapter. Professor Walter Lewin made so much sense in under 50 minutes. I can now do my homework and understand what the questions are asking me. Thank you Sir.

[@abdulmajeedmohameed6398]

Sir I am an Arabic from Sudan and I studied in China and you can't imagine how hard it was but you with your great passion and smartness in the way you teach have given my a hand and now even after I finished and went back home I still watching your videos to learn more and enjoying my self with the beauty of understanding as you said ... it is easy to see how good person you are even without the need of knowing you and it is much easer to see how much you love what you are doing and by that you are making us love it too .. let me just say you are one of my biggest example in live and believe me I don't have much and really hope to meet you one day .. wish you the beast .. thank you sir

[@lecturesbywalterlewin.they9259]

Thank you for your kind words

[@abdulmajeedmohameed6398]

Lectures by Walter Lewin. They will make you ♥ Physics. Oooh you answered me can't believe it 😊... you are welcome sir 🙏🏼

[@NovaWarrior77]

This professor is utterly awesome.

[@kushagratiwari7950]

i am literally bunking online lectures to watch this, just phenomenal, sir you are an absolute legend, :).

[@michelhenning9311]

Always when he talks about bringing a charge in his pocket to another great charge i must think of frodo carrying the ring to mordor. Thanks fot the lectures, they are making my online semesters way more fun and better to understand!

[@SoumilSahu]

It's unbelievable how many doubts of mine have been cleared just by watching this video. Teachers at my school don't even bother going in depth to explain the difference between easily confusable terms. This playlist is a life saver!! Also, I have something I would like to confirm. Is the reason why -ve charges go from low to high potential because their electrostatic potential energy decreases in the process? (Because things like to have as less energy as possible?)

[@lecturesbywalterlewin.they9259]

F=qE. F and E are vectors. if q is negative the vectors are in opposite direction. Suppose negative mass existed. They would move in the opposite direction of gravity, thus they would go UP. Yes, they would go from their high to their lower potential.

[@athuldas9350]

@@lecturesbywalterlewin.they9259 Sir if there existed a negative mass, the force will be in the opposite direction. But force is mass times acceleration. So since mass is again negative, won't the body accelerate downward as usual?

[@railspony]

@@athuldas9350 There is no "again," when you do F=ma with a negative mass you only have one negative in there. You're letting the logical conception leak into a nearby formula when you add an extra negative.

[@vishalmujmule9027]

@@athuldas9350 mass is never negative

[@indrajitdasgupta3344]

When negative Charge is at low potential , they acquire high energy (-qV) and when it is at high potential it acquires low energy. ( for eg -2 > -3 ) and it's in nature that objects always tend to move to lower energy for more stability. That's why a free negative Charge move from low Potential to high potential. This is one explanation. Another one is from the point of view of Force abovementioned.

[@yusufmoalim9506]

Physics works and makes sense when is met through Professor Walter Lewin, "my favorite lecturer". May Allah give You good health and long life! Best Wishes

[@user-mt9bk3qe3u]

Hands down the best lecture on Electrostatic potential Awesome work Sir Walter Lewin

[@sumitradebnath9665]

It was really very difficult to study during this lock-down but finally I discovered your lectures sir which are really helpful. I believe only in text book reading and my teachers guidelines. But during this lock-down I am doing online studies and your lectures really helped me. YOU MADE ME REALIZED THAT ONLINE STUDIES ARE ALSO GOOD. THANK YOU SIR

[@realistreset8336]

If I had to guess, the reason textbooks describe V in relation to the integral of E as V = - int E * dl is because they want to illustrate how the change in electric potential - gradV - is opposite that of the electric field. If potential is decreasing, E is positive; increasing, E is negative. It's not just confusing to try to understand it is that way, it's insufferable. It's so much more intuitive to explain potential as the field going from final point to initial point as is analogous to every singe text on calculus ever written. It's good to see that I'm not crazy for finding such an explanation infuriating.

[@nicolaspizarro9657]

Many thanks for this classes... you have really help me to understand the concepts of this beatiful part of physics. I'm from Chile !

[@lecturesbywalterlewin.they9259]

:)

[@rutubaldha3995]

Love it the way you teach...your lectures make me love physics even more... Thank you sir.

[@abdullahsajidasfm8383]

I used to hate physics until I came across your mezmerizing and awasome lectures. Now looking forward to go for quantum physics. Stay blessed💐

[@studywithjosh5109]

Thank you so much for creating these amazing videos. You will help Millions and Millions of Students one day. You lectures really do make me ❤️ physics. I wish I knew who you were last time I was in Cambridge because I surely would have stopped by to say hello.

[@rajranitandon1764]

Fall in Love with physics after watching your lecture

[@RiyaTomar-jd3mw]

My first lecture with you sir. It really amazed me sir, the experiments, teaching, your skill of making dotted lines and the expressions. PS-I am a JEE aspirant. thank you so much for such a wonderful lecture.

[@KumudJhaLIC]

Oh ! So wonderful . It makes me more curious about physics.You are a hero sir . You make me love physics.❤❤

[@prateek1369]

I am going to remember this lecture for the rest of my life! Thank You so much sir!

[@lecturesbywalterlewin.they9259]

nice!

[@bewakoofsparsh3441]

I am from India and I loved your lectures but I want to confess one thing in our country teachers are more focused towards theoritical knowledge we hardly have practicals in the live classes . Today I understood the importance of practicals thanks a lot sir 🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏

[@sidman1505]

I agree

[@whoatemywendys]

I love this guy, he just speaks with such passion!

[@harshmittal6461]

Sir you are great really, the things which we learn in our institutes take a lot of time teaching these things they just repeat the easy things and doesnt even explain very clearly and you just covered those things in very short time by teaching with diagrams and making everything on the board it was just amazing and very easy to remember

[@sohinighosh1002]

sir, i didn't really have a good relation with physics.. after your lectures have been strengthening my bond with it.. thank you!

[@sdrpanwar6501]

Agree with you

[@x0cx102]

The marching analogy made this video very exciting and understandable :)

[@lecturesbywalterlewin.they9259]

:)

[@fk1583]

Im only a high school didnt start my higher studies yet due to the pandemic ... but these classes and the visual representation of concepts are really helping me to deal with my entrance examinations .... thank u sir ... u r a legend .... love from India 🇮🇳🇮🇳🇮🇳

[@Sneha-fo5bf]

Professor, your way of teaching is beyond reality. This topic seemed very tough to me and after the completion of this video i was like, "wow! This topic is love!"

[@lecturesbywalterlewin.they9259]

Glad to hear that

[@jriseup7201]

Thanks for saving my semester !!

[@lecturesbywalterlewin.they9259]

:)

[@studytime9612]

@@lecturesbywalterlewin.they9259 :)

[@speedcubingandgamimg4200]

@@lecturesbywalterlewin.they9259 :)

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@@lecturesbywalterlewin.they9259 :)

[@Professor_Ray]

HOW ARE YOU DOING MAN WHERE ARE YOU IN LIFE

[@racklucifer3343]

heya...the best lecture ever...does he give lectures on ray optics??that would be really helpful.

[@nikhilnagaria2672]

They are down in 802 if you see clearly

[@tahsinahmed5019]

I am from Bangladesh sir.You really have an unique way of helping seeing physics,in a whole new way and make us love the subject. We loveeeeeyou

[@ayushmehta2323]

U R CLEARLY A GEM FOR ME SIR ...HUGE AMOUNT OF RESPECT FOR U SIR !

[@ckristie2278]

I wish my Professor for Physics 2 was you. Interesting and Fun lectures!

[@aayushiaayushi8137]

He teaches in mit.... search how to get into mit.... you will be surprised

[@muhammadsiddiqui2244]

If someone fulfill all my needs and I become free from them and I listen to these lectures......that is an ideal life for me......

[@priscilamartinezavila194]

So knowledgeable and so humble at the same time ❤

[@newagegamer1932]

clarity at its best .true gem

[@moneymindset308]

a jee aspirant life saver god bless man like this

[@MM-by6qq]

46:48 I saw your body through the electricity 😂😂😂

[@NotLegato]

these lectures are incredibly informative and entertaining, i'm learning a huge amount on each one. this course is a great precursor to my studies in electrical engineering.

[@lecturesbywalterlewin.they9259]

:)

[@rampalsingh8938]

Thanks a lot sir. I am a student of BSc physics (Hons) from India. Your lectures help me to see beyond the equations.

[@hezalraiththa1939]

Thank u professor, huge respect from india 🇮🇳

[@meryemfat]

I just finish lect 4 and i really really really enjoy it 😎, thank you so much sir ❤️❤️❤️❤️

[@lecturesbywalterlewin.they9259]

GREAT!

[@riyachauhan9317]

Sir i am from India.. i watched it for the first time sir.. but i love your lecture !! and now i am preparing for my NEET , amazing sir .. Thank you sir .. for making the concept perfectly clear !!

[@itseasyitspractical]

These Ahs in the end were so funny, I think I rewatched it a thousand times. What a professor!!!

[@karthiks9438]

sir you are on of the greatest lecturer of all times. Thanks for making me love physics

[@lecturesbywalterlewin.they9259]

thanks for your kind words

[@fahimmumand]

Thank you very much sensei, I am watching your lectures and regretting my time I spent in university. Watching your lectures really are strengthening the foundation. I do have smile on my face when I have a question after you describe a theory and immediately you ask that question and start solving it. It is like telepathy.

[@lecturesbywalterlewin.they9259]

:)

[@yonatankebede7478]

Thank you so much Dr. Lewin!

[@manaswi3]

So this video got viral recently in my area loved it! 👍🏼 Physics have never been so interesting before!

[@gubnawarrior6489]

why are u so good ? .... THE BEST EVER :)

[@mobinmk007]

Sir,Now. Am big fan of u..U r great proffessor..Ur demonstration,teaching style made me so crazy..I wish to attend ur class ..Am from Kerala,India

[@lecturesbywalterlewin.they9259]

:)

[@shishirkumar8940]

Am also from bihar

[@dyutibiswaspotterhead5268]

Professor Walter Lewin sir, i am soo blessed to have u as my teacher (online ofcourse :D) thanks a lot I am an JEE aspirant and you are really helping me a lot to understand the feeling of these concepts here I don't even have a proper teacher who can teach for such a difficult examination thanks a lot for ur support sir if I ever get chance to meet u , I would faint literally 😁😂

[@priyadarshichaudhary7905]

I loved the final demonstration of fluorescent tube with van de graff generator .

[@surindermalhotra9892]

its my dream to have a physics teacher like you 😌😌

[@ankitsonigra3085]

i wish i could attain your lecture sir ...next time if u come to INDIA i will manage anyhow to attain your leacture.. 😊

[@ZBAcademy]

The only teacher that i respect from my heart 💓.. Because he is the only teacher who shows us what the physics is in real sense rather to show us only theories of physics .. Respect.

[@pratiksahu173]

U must respect everyone.... :-)

[@abiramisundaram9432]

My fear towards this lesson had flew away after watching ur lectures.😍.u r teachings are Awesome❤️.

[@galdekel1017]

the best teacher i have ever seen

[@djtoddles8750]

28:24 U and V distinction

[@thienthanhtranoan6723]

0:20: electrostatic potential energy => U (from infinity to 1 point) (* electrostatic forces are also conservative forces) Comparison: U vs V (Do not confuse) 10:50 V in a sphere (+Graph) +Maxwell’s publication +comparison E vs V (Do not confuse) 27:00 + equipotential surfaces (never intersect) + low potetial -> high potential (q low (q>0) +Va-Vb +work - energy theorem *The important thing is the difference of Potential* 43:30 experiment with Van der Graff (*current) ------ Thanks to Walter Lewin

[@vaishnavkumars9261]

A Big Thanks to Professor Walter Lewin who not only takes us to the invaluable and unique physics classes but also Takes time to answer our doubts in the comments section below !! Hats off to you ....... Thanks A Ton !!!

[@lecturesbywalterlewin.they9259]

thank u

[@divyanshusiwach]

Professor could you please explain me the lightening of the tube? According to what I have understand, VDG creates a voltage difference b/w the ends of tube resulting in electrons flowing from lower potential to higher potential. When you touched it, voltage difference became even higher resulting in even greater flow as earth's potential is descried as 0. If I am correct up to now, I would like to know what happens when VDG is switched off suddenly. Whether electrons gathered on closer end of the tube w.r.t. VDG will flow back to Earth in a very quick time giving you a shock or anything else will happen out there.

[@syedsouban9870]

The demonstration you did at the ending of the video was awesome sir! The way you made current pass through the tube can we use the same principle to recharge batteries?

[@syedsouban9870]

I am waiting for your reply sir!

[@WeAreCamels]

Syed Souban Don't expect him to reply to everyone that will be too demanding for anyone​. He has a job and life to live. He already spends a great deal of time to make, edit, and post these videos.

[@lecturesbywalterlewin.they9259]

Would be a very inefficient (also very unpractical) way to charge batteries.

[@aastha2336]

@@WeAreCamels and he replied

[@luciaverga4750]

Great professor and marvelous ending!

[@creatorattractor4189]

They dont make teachers like this anymore that put so much passion in his teaching.

[@someone8987]

Love u....walter....May Allah bless u nd grant u health....Blessed be....From kashmir...

[@kratosislive4764]

Saalo bhosdi waalo Kabhi hum Indian he aisa bhi likh do

[@KamleshSharma-gc8jv]

0:59 is that how the actual recordings were? black and white? then later converted into colour?

[@risegaming586]

Sir your lectures are so much interesting i wanted to see all of them at this particular second

[@mikasa-wv6vv]

My journey is going to be awesome learning from you sir! ThAnK YoU 👍