Electrons at rest have magnetic fields

[TruBlu4AU]

It could be that I'm misinformed, but I heard electrons at rest have magnetic fields. I thought that magnetic fields required a charge to be traveling at velocity before a magnetic field would arise. If this is the case could someone help me out?

If an electron has a magnetic field at rest what is its strength? Or to be more specific, if we were to take the classical radius of the electron, 2.8179403267 x 10^-15m, what would the surface force due to magnetism be on the electron if we could somehow shrink ourselves to that size and stand on the electron's surface? Is there anyone who can calculate what that value would be assuming what I heard was correct?

 

[my2cts]

Electrons have a property called "spin".
With this comes a magnetic dipole moment, so an electron is a tiny permanent magnet.
Its magnetic moment has a value of about 10^-23 J/T (Bohr magneton).

 

[Dale]

Electrons have spin angular momentum and charge, so they do have an intrinsic magnetic dipole moment.

The classical radius thing is meaningless for an electron so there isn't a good answer for your other questions.

 

[TruBlu4AU]

I see guys, thanks. So electrons are like little magnets then. Is there any way to calculate their magnetic field strength?

 

[Dale]

I see guys, thanks. So electrons are like little magnets then. Is there any way to calculate their magnetic field strength?

Certainly. Here is a good starting point for an overview. https://en.m.wikipedia.org/wiki/Electron_magnetic_moment

 

[TruBlu4AU]

Electrons have spin angular momentum and charge, so they do have an intrinsic magnetic dipole moment.

The classical radius thing is meaningless for an electron so there isn't a good answer for your other questions.

I've got one more question concerning what was brought up here. If electrons are like tiny magnets with two poles of different polarity why do we view them as charged particles? Maybe there is something here I'm not quite grasping. Here's my thinking, an electron has a negative charge of roughly 1.6x10^-19 C. However, it must also have two poles of opposite polarity(like say the earth). Why don't these poles cancel out and give us a neutral particle? Is there something here I'm misunderstanding?

 

[Dale]

You seem to be mixing up magnetic poles and electrical charge. An electron has a monopolar electric field and a dipole magnetic field. Therefore it has an electric charge but not a magnetic charge (magnetic charges don't exist as far as we can tell).

 

[TruBlu4AU]

You seem to be mixing up magnetic poles and electrical charge. An electron has a monopolar electric field and a dipole magnetic field. Therefore it has an electric charge but not a magnetic charge (magnetic charges don't exist as far as we can tell).

Thank you for your reply Dalespam.

If magnetic fields don't have charge then why can we write a Beta field equation as , B=μ0/4π(Q/r2) where: Q= the charge of the field? Which again is the analog in magnetism of Coulomb's law?

 

[Dale]

That equation is not correct. Where did you get it?

Magnetic fields are caused by moving electric charges (electric current), not by separate magnetic charges.

 

[TruBlu4AU]

That equation is not correct. Where did you get it?

Magnetic fields are caused by moving electric charges (electric current), not by separate magnetic charges.

The equation came from Coulomb, the same guy who gave us Coulomb's law F=k(q1q2/r^2).

The law of force between poles was investigated by Charles Coulomb, using the same torsion balance with which he established the law of force between electric charges, and was found to be similar in form to that for charges.

In coulomb's law the the constant of proportionality was found to be k coulomb's constant which is the permittivity of free space. In the other equation the constant of proportionality was found to be μ0/4π the permeability of free space.

 

[Dale]

Please provide a specific reference for this equation.

Do you understand the difference between a monopole and a dipole? Gauss law for magnetism prohibits monopolar magnetic sources, but Gauss law permits monopolar electric sources. Thus the electron has electric charge (monopolar), and a magnetic moment (dipole).

 

[TruBlu4AU]

Please provide a specific reference for this equation.

Do you understand the difference between a monopole and a dipole? Gauss law for magnetism prohibits monopolar magnetic sources, but Gauss law permits monopolar electric sources. Thus the electron has electric charge (monopolar), and a magnetic moment (dipole).

Here's a quick link.
http://www.daviddarling.info/encyclopedia/C/Coulombs_law_for_magnets.html

 

[Useful nucleus]

Mathematical treatment of magnetism using magnetic monopoles is presented in some textbooks including Julian Schwinger classic:
https://www.amazon.com/dp/0738200565/?tag=pfamazon01-20

 

[Dale]

Here's a quick link.
http://www.daviddarling.info/encyclopedia/C/Coulombs_law_for_magnets.html

Read the third paragraph on that page. It confirms what I was saying.

Note also paragraph four which describes how the following information uses long thin magnets as shown in the figure. An electron is, to the best of our measurements, a point dipole. So the subsequent equations don't apply.