Magnetic Field?

Question

How moving charges produce Magnetic Field? What is the physics behind that?

Answer 1

All magnetic fields result, in one way or another, from moving charges. Although allowed by Maxwell's equations, which mathematically relate electric and magnetic fields via the source charges and currents (moving electric charges), the 'magnetic monopole' has never been observed. If it existed, it would be a particle responsible for the creation of a magnetic field absent an electric current.

Electric fields come from charges. So do magnetic fields, but from moving charges, or currents, which are simply a whole bunch of moving charges. In a permanent magnet, the magnetic field comes from the motion of the electrons inside the material, or, more precisely, from something called the electron spin. The electron spin is a bit like the Earth spinning on its axis.

Very serious problems arise if the charged rotating ball model of the electron is taken too literally, not the least of which is due to the fact that the electron has no known radius. That is, as far as has ever been observed experimentally, the electron behaves as a true mathematical point, or singularity, without a measurable radius. The magnetic moment, or field, of the electron arises for more subtle reasons based in quantum mechanics and the quantum theory of fields..

Answer 2

Well, I guess you already know that changing electric current causes the magnetic field.

There is no physics behind this natural phenomenon. It is like you study the electric field and get to know about the magnetic fields' existence along with.

I read that Earth is a dynamo therefore the magnetic field exists. But no reasons why an electron flow causes a magnetic field?

It is just like, how the planets were formed has been known but not why they should be there first of all? We go from the results to the methods in many cases in science. For example, if only earth supports life and not other planets in the solar system then it should be the distance, the atmosphere and so on.

Answer 3

I'm of the same mind as Harihara, but in my own words, "it's just the way it is." It's nature, and this is how nature works. We don't know the physics behind it. There are many laws of physics that just are. We can write laws and equations to describe what happens. But why or how, we don't know.

My guess is that once we get GUT (Grand Unified Theory) down pat, we'll be closer to understanding how and why the universe works the way it does. But right now we'll just have to accept certain givens. Like, gravity exists. Like, light moves at a constant speed if measured by any observer in a non-accelerating frame of reference. Like, a magnetic field is produced by a moving charge. Like, an electromagnetic field is produced by an accelerating charge. All these are natural phenomena. How or why they happen, we don't know.

Answer 4

Moving charges constitute a current Current produces magnetic field. The strength of the magnetic field depends upon a few factors in which the strength of the current is one. The current is the rate of flow of electric charges.

Answer 5

When a charge moves, we can say that current is flowing ( according to the nature of charge). Hence according to Maxwell Right hand Thumb rule a circular magnetic field is created around the charge.

Answer 6

Moving charges produce a current. That is actually the definition of current, and since any current produces a magnetic field according to the Lenz law, I guess the magnetic field is there.

Answer 7

Moving charges moving with constant speed produce static magnetic field.

Whenever there is static magnetic field, we can always find associated with it, charges moving with constant speed.

Moving charges with varying speed produce changing magetic field.

Whenever there is a varying magnetic field, we can always find associated wiht it, a varying speed of charges.

This is the phsics behind it,

If one is the cause, the other is the result. They are inseparable.

Answer 8

How? Nobody really knows. The physics behind it is observation that a current in a wire will cause deflection of a compass needle or, if strong enough, a patterned relocation of iron filings about the wire.