# Why a bar magnet or EM coil does not effect EM fields?

1. May 12, 2012

### nemesiswes

Why is it that a radio wave or a microwave is not affected by a magnetic field from a electromagnet or bar magnet? I know they are self contained and so no outside force should effect them but that I can't get my head around.

The idea I have is that since the Electromagnetic field is oscillating, the bar magnet or electromagnet actually do affect the microwaves or radios waves magnetic component. The key though is the oscillation part, since the magnetic field component of the electromagnetic wave is going north then south and so on constantly, it creates a push pull from the bar magnet or Electromagnet. Thus the push then pull creates a net force of zero causing no change to the radio wave or Microwave. However if you could sync the Electromagnets frequency with that of the microwave for example so they ware in phase with each other, you could get the Electromagnet to always cause a push or pull on the microwave's magnetic field component causing it to bend either way or toward the electromagnet.

I also think you might be able to stop the microwave entirely by canceling out it's magnetic field component. However I am really not sure on this one, I don't think it would work because even if you cancel it out, the magnetic field is still there, your just opposing it and causing a net field between the two of zero. Like two opposing Electromagnets, there fields are still there but in the middle, there is a point of zero field strength.

Also I know That since Photons are charg-less and so cannot be effected by magnetic or electric fields, but I need a more in depth explaination as to why.

Is the answer as to why light can not be bent that because electric and magnetic fields are created by the photon which is charg-less ( so no direct interaction can happen) however anything effecting the magnetic or electric component won't effect the photon either because the photon is moving at light speed and since the interaction with the magnetic field is behind or to the side of the photon, no information can make it's way back and cause a force on the photon? I say to the back or to the side because the photon can't create a magnetic field or electric field in front of it since those fields would now have moved faster then light speed and no interaction can happen before the fields are there.

So is this right.

Last edited: May 12, 2012
2. May 13, 2012

Staff Emeritus
The magnet would interfere with the radio - if you were able to shake it a few million times a second and match the radio's frequency.

3. Jul 12, 2012

### norice4u

How do you explain the interaction between photons and electromagnetism? That is how is magnetic field composed of photons particle and that these photon particle is responsible for the interaction between electron particle through an induced current?

I am really asking can you increase the amount of photons in a magnetic bar by directing a beam of light to increase the photon packets around the magnetic bar?

What is the interaction between photons and electrons? What is the characteristics of this interaction and how it differs from the other 3 interaction ( gravity, strong nuclear, weak nuclear)?

4. Jul 12, 2012

### Drakkith

Staff Emeritus
A photon is the quantum of electromagnetic radiation. This just means that when an EM wave interacts with anything it will do so in little packets of energy we call photons. So the induced current in an antenna in a radio is the result of countless little interactions between the wave and the antenna. Normally it would be described as countless photons being absorbed and adding their energy together.

A magnetic bar does not contain photons. If you were to move the bar back and forth it would produce a propagating EM wave, which would then interact through photons. Directing a beam of light at the magnet would do nothing. There are no photon packets surrounding the magnet.

The interaction between the electromagnetic force and any charged particle is complicated and requires an understanding of it along with the other 3 forces. I don't think we could hope to explain all of it here in a thread. See here: http://en.wikipedia.org/wiki/Electromagnetism