B Can we use a permanent magnet and a copper rod to create an electret?

[Wo Wala Moiz]

Electrons have a magnetic dipole moment. If a permanent magnet was held against one end of a copper rod, the delocalised electrons close to the magnet would be attracted and concentrate around the magnetic pole.

This should result in the creation of a weak electret because of the uneven electron distribution.

 

[fresh_42]

This was my first hit on Google:
https://physics.stackexchange.com/q...ets-have-an-electric-current-surrounding-them

 

[Baluncore]

A magnet can be used to sweep electrons sideways, but not to pick them up.
To make an electret requires that a charge imbalance be frozen into a solid dielectric.
Copper is not a solid dielectric.

 

[Wo Wala Moiz]

This was my first hit on Google:
https://physics.stackexchange.com/q...ets-have-an-electric-current-surrounding-them

It doesn't address the question, though, which is about using a magnet to induce an electric dipole field in a non ferromagnetic conductor like copper.

 

[Vanadium 50]

It sounds like the question you wrote is less clear than the question in your head. You may want to take another stab at it. You might also think about explaining why a generator is not the thing you are looking for.

 

[Wo Wala Moiz]

A magnet can be used to sweep electrons sideways, but not to pick them up.
To make an electret requires that a charge imbalance be frozen into a solid dielectric.
Copper is not a solid dielectric.

You say that a magnet can only sweep electrons sideways, but how can that be since electrons are not merely point charges, but also have a magnetic dipole moment?

In a uniform magnetic field, certainly an electron would only experience torque. But in a non uniform magnetic field, that is, where there is a gradient of field intensity, why wouldn't it experience attraction to a magnetic pole?

Thus if a magnet is held against a piece of copper, the delocalised electrons should have a distribution close to the magnets, due to their dipole moments.

 

[Wo Wala Moiz]

It sounds like the question you wrote is less clear than the question in your head. You may want to take another stab at it. You might also think about explaining why a generator is not the thing you are looking for.

Did you read the body with the details I provided? It's the first comment on this thread.

 

[Vanadium 50]

Here we go again - a confused readership and an OP who insists he's not confusing.

What you wrote is nonsense. A conducting rod is not a circuit Magnetic poles do not attract electric charge. The polite interpretation is that you were unclear. If you reject that, the alternatives are less polite.

 

[Wo Wala Moiz]

Here we go again - a confused readership and an OP who insists he's not confusing.

What you wrote is nonsense. A conducting rod is not a circuit Magnetic poles do not attract electric charge. The polite interpretation is that you were unclear. If you reject that, the alternatives are less polite.

I never said anything about establishing an electric current in a conducting rod. I asked whether a copper rod could be turned into an electret with magnet.
You understand what an electret is, right? It's the static electric analogue of a permanent magnet. Most people know them from their use in electret microphones.

https://en.m.wikipedia.org/wiki/Electret

Second, I never said that magnets attract stationary electric charge. The fact that you're asserting I stated things that I didn't is poor intellectual form- it shows you subconsciously insert your assumptions into what you read without even noticing that your assertions are baseless.
Electrons have a magnetic dipole moment. That makes them magnets.

https://en.m.wikipedia.org/wiki/Electron_magnetic_momentI propose another interpretation- you aren't aware of some of the things I'm talking about, and so instead of educating yourself about the terms I'm using, you're assuming that the terms are technobabble and I'm the one with misconceptions.

Now that I have hopefully reached you with the concepts you were unclear about, you can address the question properly- would a magnet induce an uneven electron distribution in a copper rod, since electrons have a magnetic field and should be attracted to the poles of a magnet?

 

[berkeman]

You understand what an electret is, right?

You do realize that you are chiding a PhD Physicist who specializes in and works in this area, right?

I'll ask you to tone down the attitude please.

 

[berkeman]

Thread paused temporarily for Moderation...

 

[berkeman]

Thread is reopened provisionally after some cleanup.

Thus if a magnet is held against a piece of copper, the delocalised electrons should have a distribution close to the magnets, due to their dipole moments.

No, as V50 said, the uniform distribution of valence electrons in the copper piece is not disturbed by a static magnetic field from your magnet.

 

[Wo Wala Moiz]

Thread is reopened provisionally after some cleanup.
No, as V50 said, the uniform distribution of valence electrons in the copper piece is not disturbed by a static magnetic field from your magnet.

V50 made his argument from the assumption that I was arguing that magnets attract electric charges.

He also assumed something about a conductor not being a circuit, for some reason.

My argument is that magnets would attract electrons due to their being magnetic dipoles. A magnet has a non uniform field, and so electrons would experience a linear force as well as the usual torque.

 

[berkeman]

My argument is that magnets would attract electrons due to their being magnetic dipoles. A magnet has a non uniform field, and so electrons would experience a linear force as well as the usual torque.

I think this is a valid question. Let's let others address this question for you.

 

[Vanadium 50]

First, one cannot simultaneously claim that one is perfectly clear and that ones readership is making unwarranted assumptions. Its one or the other.

Next, copper is diamagnetic. It is weakly repelled by a magnetic field.

Next, even if this were to work as you described, the electric force is so much bigger that once a handful of electrons were bunched together, future electrons would be repelled by them.

Next, you say you are not making a circuit. You can't have electricity without a circuit.

Finally, if we ignore all that, a household magnet might have a gradient of 10 T/m. For a 1mm wire, this is an energy of the order 10^-4 eV. This is tiny compared to ambient thermal energy, so the electrons would not stay polarized long enough to be attracted.

 

[Wo Wala Moiz]

First, one cannot simultaneously claim that one is perfectly clear and that ones readership is making unwarranted assumptions. Its one or the other.

Next, copper is diamagnetic. It is weakly repelled by a magnetic field.

Next, even if this were to work as you described, the electric force is so much bigger that once a handful of electrons were bunched together, future electrons would be repelled by them.

Next, you say you are not making a circuit. You can't have electricity without a circuit.

Finally, if we ignore all that, a household magnet might have a gradient of 10 T/m. For a 1mm wire, this is an energy of the order 10^-4 eV. This is tiny compared to ambient thermal energy, so the electrons would not stay polarized long enough to be attracted.

> First, one cannot simultaneously claim that one is perfectly clear and that ones readership is making unwarranted assumptions. Its one or the other.

[Reference to crackpot source deleted by the Mentors]

> Next, even if this were to work as you described, the electric force is so much bigger that once a handful of electrons were bunched together, future electrons would be repelled by them.

Which is why I specified that it would be a weak electret. I accounted for that.

> Next, you say you are not making a circuit. You can't have electricity without a circuit.

You cannot have an electrical current without a circuit, yes (unless it is alternating current, but that's besides the point). You do not need a circuit for generating static electricity.

After all, a typical electret is an insulator.

Once you brought the magnet away from the copper, the charge would not be retained unlike a typical electret, because the electrons would move back into place.

> Finally, if we ignore all that, a household magnet might have a gradient of 10 T/m. For a 1mm wire, this is an energy of the order 10^-4 eV. This is tiny compared to ambient thermal energy, so the electrons would not stay polarized long enough to be attracted.

I was imagining something more on the order of a large neodymium magnet. Or, if you will, a few large neodymium magnets in a halbach arrangement.

 

[berkeman]

Okay, thread will stay closed after deleting a very bad source. The question has been answered adequately.