A couple of questions about magnetism

[JRPB]

¿How do modern physicists think about magnetism?

Recently, I realized something really cool that made me re-evaluate the way I thought about magnetism. I'm not a physicist, I'm in the early process of becoming one (old cow trying out a whole new career). I had this "fieldy" notion about what magnetic forces were, and had a vague idea on how it relates to the electric field. After taking some calculus and classical mechanics, I eventually bumped into the interesting and different things that can happen when one chooses different frames of reference for a given problem.

Suppose I'm in a lonely region of space and I watch this electron zoom by. I have with me a device that measures magnetic fields. Since the electron is moving relative to me, the Ampere-Maxwell equation would say that my detector will register some magnetic field. However, if I'm moving at the same velocity parallel to the electron (same speed, same direction) my detector will not register this magnetic field. Naturally, because in my frame of reference, the charge is now at rest.

So, if an electron (or any other charged particle, for that matter) creates a condition in space called the electric field, and other charged particles feel this condition: ¿What is magnetism?* ¿How come this "force" depends on the frame of reference? ¿Am I abstracting something the wrong way? ¿Is magnetism another human convention due to our physical size?

If you know/feel/think this has been answered somewhere else, I'd appreciate any links or references.

Thanks in advance.

* A perfectly acceptable answer would be: magnetism is what happens when a e-field changes in time, that's the way nature is. However, I'm looking for some insight, if there's any to be found.

 

[Bob S]

An electron at rest creates an electric field but no magnetic field. The magnetism created by this electron when moving is due to the relativistic Lorentz transform shown in the last four lines of

http://pdg.lbl.gov/2009/reviews/rpp2009-rev-electromag-relations.pdf

where γ = 1/[1-β²]^½ and β = v/c

Bob S

[added] The very last equation in the above URL transforms a transverse radial electric field into a transverse azimuthal magnetic field.

 

[stevenb]

¿How do modern physicists think about magnetism?

... However, I'm looking for some insight, if there's any to be found.[/I]

There are many books that cover this. You are particularly interested in looking at the implications of special relativity. One good book is as follows, but there are many others.

Maxwell's Equations and the Principles of Electromagnetism , by Richard Fitzpatrick

https://www.amazon.com/dp/1934015202/?tag=pfamazon01-20

I also attached a pdf of an article that gives some insight. The author of this (Daniel V. Schroeder) recommends the book by Edward M. Purcell "Electricity and Magnetism: Berkeley Physics Course Volume 2", 2nd edition, published by McGraw-Hill.

 

[JRPB]

Thanks for the references, both. I'll definitely work my way through the article stevenb attached.

In the early 1960s, Edward M. Purcell wrote an innovative electromagnetism text (Elec-
tricity and Magnetism: Berkeley Physics Course Volume 2, published by McGraw-Hill,
now in its second edition) in which he used relativistic arguments to derive the existence
of magnetism and radiation. [...]

Heh, bullseye.

 

[mrspeedybob]

http://physics.weber.edu/schroeder/mrr/MRRtalk.html

 

[Quentin]

A related topic where magnetism and relativity crop up is the 'Faraday Paradox'. Spinning an axially magnetised bar magnet about its axis will NOT induce an emf in any nearby object, but DOES induce a radial emf in the bar magnet itself.

There are some weird and wonderful writings about the implications of this in cyberspace and I have thrown in my two cents worth on the topic in a page on my website, with video clips of some simple experiments, which taught me quite a bit. The link is:

http://www.gta.igs.net/~qbristow/Scientific/Faraday_Paradox/main_text.shtml