physics question

**Tren Bull** · 02-02-2006, 09:28 PM

i have been asked to describe in words what the physical meaning is of maxwell's equations. i know that the point of the first equation is that electric fields diverge, and that the point of the second equation is that magnetic fields always curl onto themselves (there are no magnetic monopoles) but i am having dificulty describing the main point of the third and fourth equations ( ampere's law, and faradays law). my question is not what the equations are ( i already have the integral form and the derivation of the differential form) i was wondering if anyone knows the physical meaning of ampere's law and faraday's law.

**Tren Bull** · 02-02-2006, 09:41 PM

here are the two equations im talking about. the first is amperes law, and the second is faradays law

**DSM4Life** · 02-02-2006, 09:49 PM

Well see if the proton and the electron force each other in an elliptical orbit and ...................

nevermind i am physic alliterate

**TADOLFI** · 02-02-2006, 09:50 PM

Man - I took this stuff like 20 years ago so if it helps great - if not...sorry.

Amperes Law - Had something to do with a visual of a straight wire...the tangential magnetic field around a closed loop to the current that passes through the loop - like the field around the wire.
(I had to look up tangential BTW)

Faradays had to do with changing the magnetic field of a coil wire and it's effects on voltage.

**Tren Bull** · 02-02-2006, 10:17 PM

faradays law seems strange to me because it says that the line integral of the electric field dotted into a differential length along a closed curve is equal to the negative derivative of the magnetic flux with respect to time, but maxwells second equation states that the magnetic flux always equals zero... god damn it, i really need to understand this

**samoth** · 02-02-2006, 10:27 PM

Not sure what level you're working at, but:

http://en.wikipedia.org/wiki/Maxwell_equations

Feynman's second Lecture book (buy 'em all if you're a physics major/minor)

"Geometrical Vectors" from UChicago Press (Great book geometrically describing vector relations and visualising div, curl, grad and other operations)

What school do you go to?

:cow:

**Tren Bull** · 02-02-2006, 10:30 PM

im finishing up my last semester at a community college. next semester il be going to chico state

**symatech** · 02-02-2006, 10:32 PM

Ampere's law basically says that the magnetic field which exists around a given current I, is proportional to that current. If you would like more details surrounding the equation then I'll write more.

Faraday's law is really cool. It says that a change in a magnetic field in a looped wire will generate emf in the wire. There are some neat flashlights out that utilize this very principle. You shake the flashlight which passes a magnet through a coil of wires and stores the charge so you never need batteries.

**symatech** · 02-02-2006, 10:36 PM

By the way Faraday's law is also the source of all magnetic fields. It is true in reverse as well (moving electrical point charges generate magnetic fields). Atoms which unpaired electrons in outer energy orbitals generate small magnetic fields. Put a bunch of them together (like in the center of the earth) and you generate a large magnetic field.

**Tren Bull** · 02-02-2006, 10:37 PM

Originally Posted by symatech

Ampere's law basically says that the magnetic field which exists around a given current I, is proportional to that current. If you would like more details surrounding the equation then I'll write more.

Faraday's law is really cool. It says that a change in a magnetic field in a looped wire will generate emf in the wire. There are some neat flashlights out that utilize this very principle. You shake the flashlight which passes a magnet through a coil of wires and stores the charge so you never need batteries.

thanks bro, ive been looking through all these damn web sites and none of them interpreted the meaning of these equations, they just repeted them in words.

**Tren Bull** · 02-02-2006, 10:42 PM

Originally Posted by symatech

By the way Faraday's law is also the source of all magnetic fields. It is true in reverse as well (moving electrical point charges generate magnetic fields). Atoms which unpaired electrons in outer energy orbitals generate small magnetic fields. Put a bunch of them together (like in the center of the earth) and you generate a large magnetic field.

magnetic fields are weird man. its been suggested that they are created by electron spin, but you take quantum mechanics into account (huysenberg uncertainty principle, and the shrodinger wave model) and suddenly the electron isnt considered a particle... damn im glad my major isn't focused on the molecular level of physics.

**symatech** · 02-02-2006, 10:58 PM

Originally Posted by Tren Bull

magnetic fields are weird man. its been suggested that they are created by electron spin, but you take quantum mechanics into account (huysenberg uncertainty principle, and the shrodinger wave model) and suddenly the electron isnt considered a particle... damn im glad my major isn't focused on the molecular level of physics.

it's still considered a particle. De Broglie showed that all matter is governed by or can be described by the wave particle duality. All matter can be explained either as a particle or a wave, the catch is that with subatomic particles classical mechanics doesn't accurately describe motion, partly b/c we can't make accurate enough measurements. Likewise, large matter can be explained with wave equations but the obvious condition is that it isn't required. You can calculate the wavelength of say a chevrolet moving at X m/s but it's irrelevant because you would never notice it anyways.

Quantum Mechanics is my favorite field of study, I like reading and working QM almost as much as I like whiskey...and I'm a man who likes his whiskey!

ps. the wave particle duality is one of the most beautiful things in nature. yeah i said it...im a nerd

**Tren Bull** · 02-02-2006, 11:11 PM

the way i look at it, its ok to be amazed by these things... especially if you're totally roided out.

**BeerBaron** · 02-02-2006, 11:13 PM

hit up johan, i know he took a physics class on magnetic fields and is genuinly interested in physics.

**Tren Bull** · 02-02-2006, 11:13 PM

btw, i remember telling some girl about how we defract when we walk through a doorway, or any openeing for that matter... she wasn't impressed

**Kärnfysikern** · 02-03-2006, 07:44 AM

Originally Posted by symatech

Quantum Mechanics is my favorite field of study, I like reading and working QM almost as much as I like whiskey...and I'm a man who likes his whiskey!

ps. the wave particle duality is one of the most beautiful things in nature. yeah i said it...im a nerd

NERD

I cant wait to get into QM more indeepth. The only class I have taken was a introduction to QM, nuclear and atomic physics.
I want to work with relativistic QM

**Kärnfysikern** · 02-03-2006, 07:48 AM

Originally Posted by symatech

Ampere's law basically says that the magnetic field which exists around a given current I, is proportional to that current. If you would like more details surrounding the equation then I'll write more.

Faraday's law is really cool. It says that a change in a magnetic field in a looped wire will generate emf in the wire. There are some neat flashlights out that utilize this very principle. You shake the flashlight which passes a magnet through a coil of wires and stores the charge so you never need batteries.

Thats a good description.

I have been thinking about this alot myself. My EM class was not good. We had a great professor but because of budget cut downs ect the class was REALY stressed through(especialy considering the EM field class was BEFORE we took linear algebra so we had to half ass our way through vector calculus). So I got a grasp on how to calculate EM fields but not much understanding on what the hell Im acctualy calculating.

The moment I get some time over Im going to have to go through the entire course again on my own.

**Kärnfysikern** · 02-03-2006, 07:54 AM

When I get home from my girl Il se what feynman writes in his lecture books and write it out here

**Kärnfysikern** · 02-03-2006, 08:04 AM

when talking about QM. The one thing I dont like with QM and the schrödinger equation is that it has no real physical meaning, not one that I have seen so far

.
Its just a tool to calculate probabilities of a stochastic phenomenon.

It doesnt give intimate understanding. Just a way to do calculations. I guess this is why Einstein wasnt pleased with quantum mechanics allthough it gave so accurate results that no one can deny the theory is right.

I guess the question is simply. What real wave is the schrödinger equation describing. The slim answere that its the probability that is waving isnt realy pleasing to me.

**Kärnfysikern** · 02-03-2006, 08:09 AM

Originally Posted by symatech

By the way Faraday's law is also the source of all magnetic fields. It is true in reverse as well (moving electrical point charges generate magnetic fields). Atoms which unpaired electrons in outer energy orbitals generate small magnetic fields. Put a bunch of them together (like in the center of the earth) and you generate a large magnetic field.

Do you know any advances in the magnetic carbon field? Last time I heard they could not explain how carbon can be magnetic neither with unpaired electrons or electron spins.

http://physicsweb.org/articles/world/17/11/7

***SPIKE*** · 02-03-2006, 10:37 AM

Originally Posted by symatech

Ampere's law basically says that the magnetic field which exists around a given current I, is proportional to that current.

Originally Posted by symatech

By the way Faraday's law is also the source of all magnetic fields.

Oh no I took all of this a few semesters ago. Bringing back some horrible memories, glad its all over.. Fheeeeeeeeeeeeeew

**Tren Bull** · 02-03-2006, 04:13 PM

Originally Posted by johan

when talking about QM. The one thing I dont like with QM and the schrödinger equation is that it has no real physical meaning, not one that I have seen so far

.
Its just a tool to calculate probabilities of a stochastic phenomenon.

It doesnt give intimate understanding. Just a way to do calculations. I guess this is why Einstein wasnt pleased with quantum mechanics allthough it gave so accurate results that no one can deny the theory is right.

I guess the question is simply. What real wave is the schrödinger equation describing. The slim answere that its the probability that is waving isnt realy pleasing to me.

i was under the impression that the wave in the schrodinger model represented the probable area where the particle is located.

**Tren Bull** · 02-03-2006, 04:20 PM

you know what i find is really amazing? the theory that light travels as a wave, but colapses into a particle when it hits a surface. so its not just that light has wave like properties and particle like properties, it literally is both. i really haven't studied this in detail at all though, ive only heard about it. anyone know more about this?

**kloter1** · 02-03-2006, 04:32 PM

opposites attract

**SnaX** · 02-03-2006, 05:25 PM

Powers of magnetism?

(Reminds me of a little electric motor, or a power generator.)
ah yes... paramagnetic and diamagnetic... you know you can elevate a non ferrous material such as a piece of plastic or a frog with diamagnetic fields? That's something you'll like reading into

anyhoo..
Ampere's Law says that the energy around a closed loop is proportionate to the energy flowing through the loop.

As for the faraday's law says any magnetic change around a coil wire will creat voltage, and it doesn't matter how the change occurs, it will stll produce energy.

Is this right. i don really remember all this lol... im such a goon :P

**Kärnfysikern** · 02-03-2006, 06:47 PM

Originally Posted by Tren Bull

i was under the impression that the wave in the schrodinger model represented the probable area where the particle is located.

the schrödinger equation only get a physical meaning when you normalise it. The schrödinger equation is most often a complex function and cant have any physical meaning whatsoever until its normalised.

**Kärnfysikern** · 02-03-2006, 06:49 PM

but even when you calculate probability flux/current I think its a very odd process. I cant get a physical feeling for what a probability flux is. I can just work calculations on it. But I guess its because its unnatural to think of a particle not having a fixed location at every given point in time.

**Tren Bull** · 02-03-2006, 09:12 PM

Originally Posted by johan

but even when you calculate probability flux/current I think its a very odd process. I cant get a physical feeling for what a probability flux is. I can just work calculations on it. But I guess its because its unnatural to think of a particle not having a fixed location at every given point in time.

quantum mechanics is hard to understand because its something we cant see and test without VERY expensive equipment... that and its so damn complicated

**DSM4Life** · 02-03-2006, 09:15 PM

I know how to make a vacano with bake soda and vinegar !

**Tren Bull** · 02-03-2006, 10:56 PM

Originally Posted by DSM4Life

I know how to make a vacano with bake soda and vinegar !

yea, i know how to make pipe bombs ... thats applied physics and chemistry. i need to find out how to make thermite... im sure i could find some good uses for that.

**symatech** · 02-03-2006, 10:59 PM

Quantum Mechanics is really cool imo. And I'm going to make a thread about it at another day when I have more time and motivation. It will be brother to my string theory thread years back

I'll go into detail about what I like and don't like about it, but why as a whole I enjoy it.

-------------------------------------------------------

Very interesting theory - it makes no sense at all.

Groucho Marx

I do not like it, and I am sorry I ever had anything to do with it.

Schrodinger

God does not throw dice with the cosmos

Einstein

Who are you to tell God what to do

Bohr in response to Einstein

If that turns out to be true, I'll quit physics

Max von Laue on the wave particle duality

Nobody understands quantum mechanics

Feynman

**Tren Bull** · 02-03-2006, 11:02 PM

i have heard many times by my teachers that nobody understands quantum mechanics... so far from what i have seen im believeing it.

**Kärnfysikern** · 02-04-2006, 06:03 AM

Syma how come your such a big fan of string theory??? I havent read all that much about it but I think its a very hmm unattractive theory of everything. Dont know why it just a feeling I get. Especialys since its not falsifiable in the close future

and like my theoretical physics professor said. To even work with string theory you need to be a mathematical genious. Just gifted/talented doesnt cut it when it comes to string theory

When something gets so horribly complex I dont think its right ;(

He told a story of one very bright student he had that did his doctor thesis on string theory and it got published and was well recived but after another 2 years the poor dude just gave up. He said he couldnt possibly work with the theory anymore because its so terribly complex.

I REALY hope this theory will turn out to be right
http://en.wikipedia.org/wiki/Heim-Theory
If it doesnt get falsified within the coming 3 years I think Im going to do my doctorate thesis on heim theory. The little I have read is just amazing. Especialy the particle mass predictions.