electric-currentelectromagnetismelectronsmagnetic fields
I keep hearing everywhere that magnetism and electromagnetism are different but is seems to me that when a current is moving and it creates a "magnetic field", it is just electrons repulsing other electrons and attracting protons, isn't that electromagnetism?
In a natural magnet, are not all electrons aligned pointing to the same side so that other electrons are repelled? If so this seems like regular electromagnetism to me…
Please clarify, I am a physics rookie.
Your teacher's statement that you can't talk about positive and negative magnetic charge is ... difficult.
You see, there have been no observations of any magnetic charges (which are called "magntic monopoles"), but a lot of theorists favor the existence of such criters because
If there are magnetic monopoles then they would comes in positive and negative varieties, and even though they are not monopoles the difference between the poles of a magnetic is very much the same as the difference between positive and negative electric charges.
To illustrate what I mean by the difference being like that between charge polarities, consider that electric field lines are seen as coming "out" of positive charges and going "in" to negative charges. Likewise--if we don't look inside the magnet--magnetic field lines are drawn going "out" from the north pole and "in" to the south pole. (Looking inside the magnet the situation is reverse, because in the absence of monopoles all magnetic field lines are loops, but I don't want to get into that.)
So then you get moving electrons and all of a sudden you have a "magnetic" field.
But at the same time if you take a magnetic dipole (a magnet as we know it) and move it around you will all of sudden get an electric field.
It was a great step forward in the history of physics when these two observations were combined in one electromagnetic theory in Maxwell's equations..
Changing electric fields generate magnetic fields and changing magnetic fields generate electric fields.
The only difference between these two exists in the elementary quantum of the field. The electric field is a pole, the magnetic field is a dipole in nature, magnetic monopoles though acceptable by the theories, have not been found.
Electric dipoles exist in symmetry with the magnetic dipoles:
$\hspace{50px}$
$\hspace{50px}$
.$$
\begin{array}{c} \textit{electric dipole field lines} \\ \hspace{250px} \end{array}
\hspace{50px}
\begin{array}{c} \textit{magnetic dipole field lines} \\ \hspace{250px} \end{array}
$$
- but there's no ACTUAL inherent magnetic force created, is there?
There is symmetry in electric and magnetic forces
(the next is number 2 in the question)
- Isn't magnetism just a term we use to refer to the outcomes we observe when you take a regular electric field and move it relative to some object?
Historically magnetism was observed in ancient times in minerals coming from Magnesia, a region in Asia Minor. Hence the name. Nothing to do with obvious moving electric fields.
After Maxwell's equation and the discovery of the atomic nature of matter the small magnetic dipoles within the magnetic materials building up the permanent magnets were discovered.
- Electrons tend to be in states where their net charge is offset by an equivalent number of protons, thus there is no observable net charge on nearby bodies. If an electron current is moving through a wire, would this create fluctuating degrees of local net charge? If that's the case, is magnetism just what happens when electron movement creates a net charge that has an impact on other objects? If this is correct, does magnetism always involve a net charge created by electron movement?
No. See answer to 2. Changing magnetic fields create electric fields and vice versa. No net charges involved.
- If my statement in #2 is true, then what exactly are the observable differences between an electric field and a magnetic field? Assuming #3 is correct, then the net positive or negative force created would be attractive or repulsive to magnets because they have localized net charges in their poles, correct? Whereas a standard electric field doesn't imply a net force, and thus it wouldn't be attractive or repulsive? A magnetic field would also be attractive or repulsive to some metals because of the special freedom of movement that their electrons have?
No. A magnetic field interacts to firs order with the magnetic dipole field of atoms. Some have strong ones some have none. A moving magnetic field will interact with the electric field it generates with the electrons in a current.
- If i could take any object with a net charge, (i.e. a magnet), even if it's sitting still and not moving, isn't that an example of a magnetic field?
A magnet has zero electric charge usually, unless particularly charged by a battery or whatnot. It has a magnetic dipole which will interact with magnetic fields directly. See link above.
- I just generally don't understand why moving electrons create magnetism (unless i was correct in my net charge hypothesis) and I don't understand the exact difference between electrostatic and magnetic fields.
It is an observational fact, an experimental fact, on which classical electromagnetic theory is based, and the quantum one. Facts are to be accepted and the mathematics of the theories fitting the facts allow predictions and manipulations which in the case of electromagnetism are very accurate and successful, including this web page we are communicating with.
Best Answer
Your instincts are spot on. While it’s still common for people to refer to electricity and magnetism as different phenomena, they’ve been formally unified since Maxwell’s 1873 paper on the subject, and they were known to be intimately related for decades before that through Faraday’s work among others. “Electromagnetism” covers all of the behavior of charges whether they’re at rest (static electricity) or in motion relative to an observer and/or each other (magnetism).
Like you said, it’s all just electrons repelling other electrons and attracting protons. The neat thing about electrons in motion (which we still refer to as magnetism to make it clear that we’re talking about moving electrons) is that it’s special relativity in practice. In our daily lives we don’t typically get to see the effect of length contraction that Einstein predicted for moving bodies, but we do get to see its effect with currents and magnetism because electrons move so fast: a magnet is applied special relativity in the palm of your hand! (Be careful about trying to contain a fusion reaction with it though, that’s tricky business ;)
Natural magnetism and ferromagnetism is a bit more complicated, and involves quantum mechanics, but you have the gist of it: when regions (called “domains”) within a material can be forced to retain a predominance of electron spin alignments around one direction of an axis more than the other, the material is said to have magnetic polarization, which can produce powerful effects. But even in our strongest magnets, only a tiny fraction of the electrons in the material are spinning more in one direction around the axis of polarization than the other – if we could somehow get –all- of those electrons aligned to spin in one direction the forces would be almost inconceivably powerful...