# Electromagnetic materials

• physior
In summary: The electromagnetic interaction can set everything in motion in some way. What do you mean with "lightest material"? Smallest mass, lowest density, something else?I am looking for a strong material but lightweight, that can be set in motion under electromagnetic field OR can be induced into a magnet if electrifiedThat is still very vague. Even contact interactions ("pushing things") are influenced by electromagnetic interactions.

#### physior

hello

which is the lightest material that electromagnetism can set it in motion?

thanks!

The electromagnetic interaction can set everything in motion in some way. What do you mean with "lightest material"? Smallest mass, lowest density, something else?

I am looking for a strong material but lightweight, that can be set in motion under electromagnetic field OR can be induced into a magnet if electrified

That is still very vague. Even contact interactions ("pushing things") are influenced by electromagnetic interactions.

What do you want to do?

basically a kind of motor

I have a rotating disc
I want to link that disc to another disc and make them both rotating together
but I want them not to be connected mechanically, but electromagnetically
I want by electrifying them somehow, to make them rotate as one (either attached physically or not), but secured together electromagnetically

Are the disks next to each other? Permanent magnets should be the easiest solution. Replace them by electromagnets on one disk if you want to be able to switch the connection.
You won't get much power transfer without a mechanical connection or very large and heavy magnets.

the electromagnetic interaction can only move things that have an electrical charge, right?

All atoms have electric charges, both positive and negative ones. So basically everything interacts with electromagnetic fields, if the fields are strong enough. Even things that "normally" are not magnetic or electrically charged.

To make an electric motor out of two discs, you would have to attach a series of magnets with opposing polarities on one disk, and a set of coils on the other, and then
power the coils with the right AC frequency.

http://en.wikipedia.org/wiki/Brushless_electric_motor

mfb said:
Are the disks next to each other? Permanent magnets should be the easiest solution. Replace them by electromagnets on one disk if you want to be able to switch the connection.
You won't get much power transfer without a mechanical connection or very large and heavy magnets.

large and heavy magnets or high currents and high voltages?
I don't want them to be permanently magnetic, that's why I want them to be electromagnetic

M Quack said:
All atoms have electric charges, both positive and negative ones. So basically everything interacts with electromagnetic fields, if the fields are strong enough. Even things that "normally" are not magnetic or electrically

neutrons don't have electric charge

physior said:
large and heavy magnets or high currents and high voltages?
Depends on the details of the setup, maybe all together.
Probably impractical, but hard to tell without any estimate of the size and scope of the project.

@Dinis Oliveira: Free neutrons are unstable, so in normal matter they are always bound in nuclei with protons, and then you have charged objects around again. In addition, neutrons contain quarks, and those are charged.

mfb said:
@Dinis Oliveira: Free neutrons are unstable, so in normal matter they are always bound in nuclei with protons, and then you have charged objects around again. In addition, neutrons contain quarks, and those are charged.

what does unstable mean here?

They decay (to proton+electron+neutrino).

mfb said:
They decay (to proton+electron+neutrino).

and that proton and electron won't form an atom?

Extremely rarely, usually the particles shoot away with high energy that got released in the decay. Where is the relevance for the topic? Please open a separate thread if you have more questions about neutron decays.

physior, davenn and M Quack