Electromagnet

[Nameo]

What would cause a metal bair to create a buzzing sensation when held close to an electromagnet? And what are advantages of an electromagnet over a permanent magnet?

[mrbatfink]

I would guess the buzzing sound comes from the vibration of the pliers this can happen due to the interacting magnetic fields.

Advantage of electromagnet: Youg can turn it off.

you can also vary how powerfull it is.

[stanleyman]

This would only happen with alternating current, the buzzing is the frequency of the supply, in UK 50 htz.

Permanent and electromagnets have different uses, for example a loud speaker or small cheap DC motor would use permanent magnets and electromagnets for the permanent and variable fields or armature. Larger and more powerful machines would need be all electromagnets.

[steveb]

you may also get this if you are using DC supply from a standard college powerpack plugged into british mains, as it's not "true" DC