Lec 27 | MIT 8.02 Electricity and Magnetism, Spring 2002

[RobertMOdell]

25:27 How in the world can it be a "plane wave" in the y direction? It must have some limit to the extent of its distance. I really don't see the leap of faith to assume it is constant in the y direction as far as you would like it to be. Even at 100's of kilometers? Light years? If not, then how far? Anyone know? Thanks.

[MrQuuem]

The end was very amusing, but I don't think he would be really heard by anyone outside that class. I mean, I guess it's such a low potency antenna, that the signal doesn't go a very long distance before being completly dumped. Therefore, only that radio very close to the antenna can get the signal.

[oshmunnies]

Does anyone know what lecture Dr. Lewin talks about inductance and magnetic field energy??

[H4RDJuMP43V3R]

NERD

[nbsr1]

Can anyone explain why E and B of EM waves are always in phase? An intuitive interpretation of Maxwell's equations would be that they should be shifted 90deg in respect to each other (since each is proportional to the other's time derivative).

I know that's what the math says, just can't picture it in my head.

[DemonDark824]

that was ballin'

[tylerjuno]

Search: Mythbusters Glass Voice 3/3 -- and if you skip to 4:23 you can see the man break a wineglass with only his voice!

[kotofu]

@tylerjuno Mythbusters used crystal glass which is thinner that ''normal'' glass, so easier to break. As you may also remember, they tried a lot of times. That is because some glasses contain more faults in them than others and that helps in breaking them. I think what the teacher meant is that an average more sturdy glass cannot be broken by an human voice alone.

nonetheless, the Mythbusters' episode was quite impressive.

[xellossaxon]

very, very strange way to write Maxwell's equations and there is a lot of non-mathematical talk, too. if that is classic MIT-style it is dissapointing, especially for a German student of electrical engineering, physics or mathematics. feels like physics lectures in the 9th grade at a high school and not like advanced teaching at a university.

[correodefelipe]

Yes it is a strange way to write the Maxwell eqs, but is it a wrong way?

Opossite to you, I believe this is a great class. Maxwell eqs can be read in any EM book. But after this lecture you do have the will to read those books, that's what makes the difference.

[jmsantander1]

@xellossaxon Well, this is a freshmen course, and I actually think that the style that Lewin uses is perfect: engaging, fun, and concept-driven.

I've seen tons of "math addicts" not being able to discuss even the most basic physical processes, simply because they don't know what they're doing when doing the math (there're exceptions, of course)

Math is a great tool, but we're talking about physics here. I'm just giving my opinion on what should be taught to the freshmen.

[vitaminasHM]

I also think it is a great class... I'm no math head, but I do love physics and electrical engineering, and this is a great class.

[Diemedes]

@xellossaxon

First of all, how to you define a "strange" or "normal" way of writing Maxwell's equations? If the information contained within the equations is the same, then there can be no "good", "bad", "weird" or "normal" way to write them.

Also, this class is a "General Institute Requirement" (GIR) so naturally the level is not on par with more advanced lectures (which exist) of Physics or Electrical Engineering students.

[eclipse245]

Jeeeeeez. Physics is great. Grade 12 physics next year :D

[freethisone]

can u name a singularity? the fact is magnetism, and electromagnetism are that singularity. that my friend we can be sure of..

the pyramids display the science as if they new how to calculate, and theorize with pictures.

alfha x ( omega ) in greek letter form.

sigma, + vector ,  in the direction of X.

[islespatrick]

I am so glad i am out of physics. Now i can learn all of this online and get an A next year.

[mrgm1381]

really inspiring, Dr. Luin.

[goodluckpeace44]

GOOD BLESS WALTER LEWIN!

[peppoj]

i lost track right about here 27:45 :S

[b00n707]

he is just inserting the time derivative into the integral and calculating the first derivative of a sin(g(t))??

what so hard about it?

[spiderman15000]

thank u very mushto uplaoding the video

i wish the teacher speak fransh or arabic i can understend better

[flipster12000]

You need to determine the resonant frequency of each glass. Each wine glass is different at least slightly. Mythbusters proved it could be done with just a human voice with no electronic help. If you must have help, put a board with a 1.5 inch hole in it in front of the speaker. Then, put a coffee straw in the glass (the straw will jump when you are close to the resonant frequency) Tap the glass with a pencil so you can hear what pitch you need. They should be made from lead crystal.

[LegEndone1]

HAHAHAHAHAHAH nice

an thankx for the props on Tacoma hahah

[goodluckpeace44]

man is this possible? radio waves are encoded.

[LevKozlodoev]

shiiiit, at a school like that ya feel like you're a part of something big

[hnhzsy123]

如果有字幕就更好了.

[hnhzsy123]

如果有字幕就更好了.