# Magnetic Field generated by a wire

1. Mar 8, 2010

### Ravui

So my notes detail how to find the direction of the magnetic field (right-hand grip rule), but how exactly are these magnetic fields produced? They can't just spontaneously come into existence just because there is a current through a wire, right? What properties allow them to come into being?

2. Mar 8, 2010

### Ravui

I checked up wiki already and came across this :

The magnetic moment is due to

(1) motion of electric charges, such as electric currents, and (2) the intrinsic magnetism of elementary particles, such as the electron.

I don't exactly understand what is i)the magnetic moment and ii)the intrinsic magnetism.

Oh and one more thing, is the 'motion of electric charges' referring to the electron spin?

I'm grade 12 so I'd appreciate it if someone would explain it in terms I'd understand.

Thanks :)

3. Mar 8, 2010

### jfy4

Well you kind of already nailed it. Current densities are responsible for the magnetic field. Both $$J$$ and $$\dot{J}$$. The motion of charges, linear motion, spinning ( quantum and angular), and periodic all produce magnetc fields.

4. Mar 8, 2010

### luxiaolei

As we know from relativity, If a electron is in your rest frame, and I am moving towards that electron, then you will NOT fell the magnetic field, and I WILL. Strange? then you may start to understand what is magnetic field..

5. Mar 8, 2010

### Staff: Mentor

For that matter, how exactly are electric fields produced? They can't just spontaneously come into existence just because there is a charge located somewhere, right?

In both cases, the existence of the field is a postulate of classical electrodynamics. Maxwell's equations tell us the relationships between fields, charges and currents, but do not include an underlying mechanism.