what is an electirc field / a magnetic field ?

does magnetic field occupy space

well .. actually i have 2 questions.

1:
for example, we cant see 'AIR' but we can feel it , and we can also understand it in terms of mixture of molecules of gases, which are made from atoms of different kinds of basic chemical elements. all i want to say .. we can understand the nature of MATTERS like AIR and electric CURRENT.
what is an magnetic field ? i am sure, they are not made from electrons or somthing like them ! if we bring two magnets of same polarity very close to eachother, we feel some kind of repulsive force. what is this, which i can feel but cant understand, like the example of AIR given above ?

2:
we know that light has both natures, elect. magnetic and photon.
i can understand the travelling of light in vaccume in sence of photones ..energy packets, like a stream, comming from a light source and thus it dose not need any medium and can travell through vaccume where nothing can help it or resist it.
sound waves can only travell trough a medium ( water, air etc etc ).

what about electromagnetic waves ? these are certanly not photons (are they ?).
every thing, like sound wave, current.. need some medium for travelling. how can EM waves travell throug vaccume ?

my these questions may seem some complex or even dumb, but if sombody can clear me .. i'll be very happy and thankfull.

regards

field perpetuates in vacuum

I think for best answers to your questions you could try GOOGLE ..
Examples here:

**broken link removed**
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfie.html

abt electric field

thanks alot for you suggestion about google and given links.

but unfortunately i couldn't find the answers of my questions there.

my question was about the NATURE (physical, chemical etc etc) of magnetic field, and
the way, how and why an EM wave can travell thourhg space (vaccume).

electirc field

Well you feel AIR because molecules in the air hit your skin thus losing momentum.
You feel something if your senses are capable of detecting their effect directly.
Magnetic and electric fields have no materialistic nature. We are also not equipped with sensors to detect them.

Magnetic field is produced by electrons spinning around axes which are parallel to each other.

Light is also an electromagnetic wave :wink:

Light consists of two field moving in the vacuum perpendicular to each other; magnetic and electric.
The nature of light is unknown. It sometimes behaves as a particle having mass; photon. In other cases it is an electromagntic wave witout any mass.
Who knows what explanation of light does the future hold. :wink:

you can see a magnetic field in the air

Magnetic field is a space around where you can measure and feel magnetic dynamic force. You have formula for it.
Similar is for electric and electrstatic field.

electromagnetism magnetism electrism

Well my friend,
the physics of the 20th century is based on your two questions.
You are asking what is the true nature of a field - in your case the magnetic field. Have you asked your self what is the nature of the electronic field? Why these two fields are different and why we call them fields?
These are questions that are coming up in the first lecture for electrism and magnetism.
The answer is that we don't know what is a field. Yes, we can sense it - on way or another- but we don't know WHAT it is. The definition of the field has as follows:
Field is the place in spece where if we put an electron( electic field), a magnet (magnetic field), a mass ( gravitation field) then a force from the existing field will be applied to it an it will atrract or push it away ( in gravitation field only attraction tooks place). This happens because the "thing" we put into the field has its own field that reacts with the original field we want to test.
So the big question what is a field is becoming : What is the force? And why forse is applied even in empty spaces ( vacum) ?
I don't have the answer and neither physics has it yet. But it is a good question to make you start reading Physics. Try Haliday- Resnic for start. Then you can upgrade...

D.

what makes somthing magnetic?

Have you asked your self what is the nature of the electronic field? Why these two fields are different and why we call them fields?

Click to expand...

as far as i have understand it, magnetic field is produced because of some spesific settings of electrons in the chemical structure of that perticular substance ( the magnet ). every substance has magnetic properties, but these are electrons, which either produce or cancel it with the help of each other.

Field is the place in spece where if we put an electron( electic field), a magnet (magnetic field), a mass ( gravitation field) then a force from the existing field will be applied to it an it will atrract or push it away ( in gravitation field only attraction tooks place). This happens because the "thing" we put into the field has its own field that reacts with the original field we want to test.
So the big question what is a field is becoming : What is the force? And why forse is applied even in empty spaces ( vacum) ?

Click to expand...

being spesific.. it is not just some kind of FORCE by any mean .. a FORCE can be applied by (just for example) high pressure of a gas, comming out from some cylender. again, we can understand by means of its molecules .. these are moleculs (FORCES's physical nature) who are comming out with great velocity and so applying some FORCE. in case of manetic or electromagnetic force.. the exact physical nature is not know to me, and that was the very question.

You feel something if your senses are capable of detecting their effect directly.
Magnetic and electric fields have no materialistic nature. We are also not equipped with sensors to detect them.

Click to expand...

perhaps, this is the correct answer that we are simply not aware of its materialistic nature, like of AIR or LIGHT, but we can certainly detect them


now to the second question:

i've given the example of LIGHT for traveling.. means, from poing A ot B, in terms of a stream of photons, again, meanig that there is some source light which practically throws energy packets (photons) in every possible direction, just like air, compressed in a cylender, comming from its nozzle fitted it.
how can electromagnetic WAVE can travell ( meaning, from one antenna to the other, located 500 kM apart) ?
as i can recive signals on my mobile phone in my room, located in very complex geomtric structure, shows that those signals follow simple reflection rules in order to come to my mobile phone. they (EM waves) are not somthing like photons or molecules, which can travel like beam from a perticular source and land to some spesific point (like the antenna of my mobile phone.. just an example).

so, how exacty do they cover the distance ?

feel magnetic field

Still my friend you are missing the physical meaning.
I tried to say that we don't know the nature of force, fields etc. We just know that force is there because to electrons moving, chemical structure of magnets, "hills" and "valeys" ( loops if my english is correct) in the time- space continuance, we can sense them as we can sence air or water ( in a different way of course), but we DON'T KNOW WHAT IS THERE NATURE! This makes things complex, I know, but it is the question of the next millenium. It is not simple like air or water. Think of this: What makes air exists? Why molecules of air fly around in less dense structure than water or any solid? Are there fields inside the molecules responsible for keeping air in this specific format? On the other hand think of radiatio. Any radiation, not only the nuclear one; Is it like air? Can we sense it with the human senses? No. Can we see its results in the enviroment surrunding us? Not right away. Why? Because radiation doesn't interracts whith what we call the macrocosm, the place we can sense with our human senses, but with the microcosm, the place we noticed its existance just 100 years ago or so.
How can radiation travel for instance from sun to the earth with no contact matterial inbetween? You have to ask your self: Does a photon has mass or not? A photon holds all the characteristics of the radiation ( the EM wave or whatever you want to call it). It travels with the speed of light but it doesn't have mass. On the other hand, it has speed and if crashes on a metal plate then either stops and the atoms of the plate absorb its energy. Therefore it has the p ( you knoe p=mxv, I can't remember the p word) . But then it has mass! Or not? Quantum mechanics tries to answer this question.
EM Fields, photons creating them etc are not always subject to reflections due to objects of our macrocosm. I.E. if the photons carrying the message of your girlfriend that she emmited from her mobile phone, meet a glass wall you will certainly receive it. But instead of the glass wall you were hidden 100m inside the earth, or in a building with heavy armoour you won't here from her, don't wait her SMS.
Why this happens? Because EM waves travel obaying roules that have to do with their propagation through matter not our prespective of propagation through matter!.
D.

donkey41 said:

well .. actually i have 2 questions.

what about electromagnetic waves ? these are certanly not photons (are they ?).
every thing, like sound wave, current.. need some medium for travelling. how can EM waves travell throug vaccume ?

my these questions may seem some complex or even dumb, but if sombody can clear me .. i'll be very happy and thankfull.

regards

Click to expand...

as far as this question is concerned, my view is that, electromagnetic waves travel in the form of electric and magnetic fields.. i mean with only a phase shift between them. actually.. first u talked abt electric "field" and magnetic "field" and then suddenly to electromagnetic "waves"... i couldnt correlate as to y u had that "fields" to be spoken to say abt this...

and, my suggestion is, u could get the answer for numerous other questions including this one at

/http://www.physlink.com

that s the best one i have ever seen for physics.. lords answering the questions!

some of the questions i have seen lead me dumbfounded are..

1) wat s the velocity with which we must travel so that red light of the signal appears green! (these were the questions i saw in my school days)

2) light s electromagnetic waves.. electric and magnetic fields alternate.. then y not magnets get attracted or repeled when a torch or heavy source of lght is on.

3) Earth is expanding.. from some bla bla theories.. does this mean, the distance between (x ) and increases over years.. and the answer was "yes"... thee was a proof!

and goes on and on!!!!

tehre are many many... i would recommend this to all!

good luck and if u get the answers elsewhere.. donr forget to post here!


/cedance

Magnetic field is a space around where you can measure and feel magnetic dynamic force. You have formula for it.
Similar is for electric and electrstatic field.

Click to expand...

i agree with this opinion, just like gravity field it's can olso travelled on vaccum

i agree with this opinion, just like gravity field it's can olso travelled on vaccum

Click to expand...

Field doesn't travel, it just exist in the space that the producer of the fiels exist and surrund the producing "thing" isotropic , that means with the same way to all directions. If the producer travels, it travels with it, if it is static and not alternating, it will be static and not alternating, if it is alternating it will change also (take for instance the magnetic field surrounding an electromagnet: if we switch the magnet on and off so does the fiels around it. If we keep it stable, the field will be stable in the certain space, if we move the field will move with it.

As for the phase shift of the electromagnetic waves, if memory serves well, the two fields are perpendicular - that is with phase shift of 90 degrees- . Why?
My friend you certainl have to read Physics from scratch...
D.

to arunmit168:

you have perhaps mixed my 2 questions.

the first Q. was about the PHYSICAL nature of MAGNETIC FILED OR ELECTRICAL FIELD (both FIELDS are in questions, but if i could get any one answer, it would be enough for new, perhaps).

the second Q. was about HOW A SIGNAL, IN FORM OF ELECTROMANETIC WAVE CAN TRAVEL IN VACCUME. to understand my Q. better, let us see it in contrast of a signal, traveling in a wire .. there are free electrons in a conducting wire , which basically help a current of electrons to flow which ultimatly help a signal to flow or travel ... in a WIRE. in vaccume current can not flow and hence can not carray a signal (in normal circumstances). we use EM to send signals. but I dont see, and eventually cant understand, any helping media in vaccume for EM to travell.

these are tow different .. totaly independed of each other .. questions.

thanks.

PS:
it's just about asking and understandig about knowledge.. it is 100 % possible that at some point, i simply dont get any thing what you may try to clear me (and you have right).. which is actually my fault .. but that's how it goes.

Well donkey here how it is:

EM Waves don't need a media to travel! EM Waves are travelling in order to keep the impulse of a system that created them constant.
Take an astronaut - or cosmonaut in the Soviet dictionary-. If he troughs away a wrench during his presens in empty space will he move or not? what will happen to the wrench?
The cosmonaut will move in the opposite direction of the wrench and with velocity proportional to the velocity of the wrench in order to keep impulse of the system wrench - cosmonaut constant!
Same with the photons; Photons are produced in order the impulse of the mother- system to be constant. They travel in space, in vacum or in dence matter - depending on the system, they exchange energy they stop or they are being alter. They don't need a media to be propagated. They are matter themselves. We say " Space is a big vacum" but we don't specify what matter is that fills space. Matter is not only earth, dust, iron, man etc. Matter is also energy. Presence of energy declairs presence of matter. Therefore matter is photons in the form of small balls or in the form of Em waves. So they occupy space. The empty space. The vacume. Does Earth moves should be your initial question. And if Earth moves how is that possible to move in the empty space, without any media helping its movement?
I think by now you ' ve got the idea.
D.

A field is a region or space where a charge experiences a force.. in simple words. If u can understand elec field, its not very tought to perceive Mag field as well. To demonstrate mag field, take a magnet and place some iron filings on a piece of paper. move the magnet closer to the iron filings and u will see tht they align thmselevs wrt the field. draw traces and u can SEE mag field.
Coming to ur second question, Light itself is an EM wave.. the properties of EM waves are satisfied by light. So, ur ques i guess is answered.
Abhi

They are real matters can be justified by experiments.

in a one word
the electric and magnetic field are state in the space that force to any charge or cuurent in this space .
that is the state and human body don't take it under safty margin.

Interesting questions ! Very basic and simple but cool
Please refer to Electomagnetism by William Hayt for first question.
and for second question do read any book by Albert Einstien.

And why forse is applied even in empty spaces ( vacum) ?

Click to expand...

Traveling with speed of light therefore no mass or empty. But it has to do with or related to the relativity these fields exist in that particular domain?

Safe bet to say is yes because is proven this thing is true! Earth magnetic field exert force on every force from cosmos protecting earth for example.
Again does it has to do with the relativity these fields exist in comparision to the rest? Most likely yes.

This happens inside earth too but imagine the speed they travel. As close to light speed as close to their "home domain".

Field doesn't travel, it just exist in the space that the producer of the fiels exist and surrund the producing "thing" isotropic

Click to expand...

Moving back to Newton if something is given a force or energy to perpetuate in vacuum when there is no "friction" does it mean the field will stay where it was created? No matter how small are particles and at what speed they are traveling priciple of inertia always is valid and no one so far has challenged it.

donkey41 said:

the second Q. was about HOW A SIGNAL, IN FORM OF ELECTROMANETIC WAVE CAN TRAVEL IN VACCUME. to understand my Q. better, let us see it in contrast of a signal, traveling in a wire .. there are free electrons in a conducting wire , which basically help a current of electrons to flow which ultimatly help a signal to flow or travel ... in a WIRE. in vaccume current can not flow and hence can not carray a signal (in normal circumstances). we use EM to send signals. but I dont see, and eventually cant understand, any helping media in vaccume for EM to travell.

Click to expand...

I guess I can try my hand out with this travelling part
To understand physically why an EM wave travels from 1 antenna to the other, consider the cause that produces it in the 1st place. We produce EM waves (Radio Frequency) by creating oscillating currents in a circuit and antenna. And since we agree that a current in a wire has a magnetic field it is understood that the magnetic field along with the current will be oscillating in value around the antenna. Then consider that the very famous Maxwell's equations say that the changing Electric field produces a Magnetic field and a changing Magnetic field produces an electric field. So here we have a changing magnetic field and so it is expected that it will create a Electric field which will also be oscillating. That Electric field will in turn produce a magnetic field. and thus this continues and we get a travelling wave !
As we know a field requires no medium to exist, so obviously an EM wave will require no medium to propagate, like a current in a wire.
I hope my post was more clarifying and helpful.

aryajur said:

We produce EM waves (Radio Frequency) by creating oscillating currents in a circuit and antenna. And since we agree that a current in a wire has a magnetic field it is understood that the magnetic field along with the current will be oscillating in value around the antenna. Then consider that the very famous Maxwell's equations say that the changing Electric field produces a Magnetic field and a changing Magnetic field produces an electric field. So here we have a changing magnetic field and so it is expected that it will create a Electric field which will also be oscillating. That Electric field will in turn produce a magnetic field. and thus this continues and we get a travelling wave !

Click to expand...

that's pretty much clearer answer .. now i have to dig, what sir maxwell has said about this topid.


thanks