# Re: Permanent Magnets

Hi all,
I have this simple question that I never really understood. A permanent magnet generates a magnetic field around itself. Is there an electromagnetic wave propagation associated with this permanent magnet? If so, what is the frequency of the wave?

Thanks,
Mike

Under current knowlege, the frequency is zero(it does not alternate with a permanent magnet) but the propagation of the magnetic field is at the speed of light.

chroot
Staff Emeritus
Gold Member
The field is static and unchanging (magnetostatic) if the magnet is not moved. If you begin shaking it, then the field undergoes an oscillation with the frequency of the shaking.

- Warren

HallsofIvy
Homework Helper
In other words, a "wave" occurs when the field changes. A regular change in a magnetic field causes a regularly changing electric field which produces a regularly changing magnetic field which produces .... (that's why the waves are called electromagnetic waves). With a permanent magnet, there is no changing field and so no wave.

Hi all,

In one of the books I'm reading, it says that shields are only used in the presence of alternating fields. However, in some websites, I see people using magnetic shields for permanent magnets which has a magnetostatic field. I ran some simulations, and the filed of a permanent magnet seems to be shielded by a layer of nickel. So, who's telling the truth?

Thanks,
Michael