Support NeoGAF

[Grildon Tundy]

I'm working on a project where I'd like for an electromagnet to be able to quickly go from attract to repel at the flip of a switch. So I bought this to tinker with:

Amazon.com: uxcell 12V DC 180N Electric Lifting Magnet Electromagnet Solenoid Lift Holding : Industrial & Scientific

Buy uxcell 12V DC 180N Electric Lifting Magnet Electromagnet Solenoid Lift Holding: Solenoids - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

It's a DC electromagnet with a DC power source. I thought I could simply take the two wires of the electromagnet, plug them in (e.g., first wire in positive; second in negative) and get "attract". Then if I switched the wires (first wire in negative; second wire in positive), I'd get "repel".

However, the electromagnet seems to attract no matter what from all angles or sides. I've tried coupling it with refrigerator magnets, rare earth magnets, and metal. In some cases it's may be a little stronger one way than the other, but I was looking for a total push/pull switch.

Anybody know what I'm missing or how I could accomplish what I'm trying to do another way? I've tried asking ChatGPT but I still can't wrap my head around why switching the wires doesn't switch the effect.

 

[Con-Z-epT]

An electromagnet can repel another magnet, whether permanent or also electromagnet, but not normal metal.

A magnet cannot attract every metal either. It can only attract ferromagnetic materials.

When a magnet comes close to a ferromagnetic substance such as iron, the so-called elementary magnets in the iron are aligned with the magnetic field of the approaching magnet, so that the piece of iron itself becomes the magnet and the north pole of the normal magnet and the south pole of the iron are in line with each other opposite and get attracted. (Of course, the other way around is also possible)

If you reverse the polarity of the current in the electromagnet, the magnetic field in the electromagnet is also reversed, which repels the other substance for a very short time, but then also reverses the magnetic field in the substance, so that the electromagnet attracts the other substance again.

The only solution would be to run a current through the other substance in the opposite direction to that in the electromagnet, but that means you would just build another electromagnet out of the substance.

In short, it is not possible. But i'm not an expert and also needed to ask an electrician at work.

 

[Con-Z-epT]

 

[StreetsofBeige]

If you knew my dad, he’d probably be able to give you an answer as he did shit like that in his career. AC currents, DC currents etc…. When as a kid all I cared about was which classmates were good looking and what channel is the hockey game on tonight.

But looks like conzept gave you a nice answer.

 

[Cyberpunkd]

An electromagnet can repel another magnet, whether permanent or also electromagnet, but not normal metal.

A magnet cannot attract every metal either. It can only attract ferromagnetic materials.

When a magnet comes close to a ferromagnetic substance such as iron, the so-called elementary magnets in the iron are aligned with the magnetic field of the approaching magnet, so that the piece of iron itself becomes the magnet and the north pole of the normal magnet and the south pole of the iron are in line with each other opposite and get attracted. (Of course, the other way around is also possible)

If you reverse the polarity of the current in the electromagnet, the magnetic field in the electromagnet is also reversed, which repels the other substance for a very short time, but then also reverses the magnetic field in the substance, so that the electromagnet attracts the other substance again.

The only solution would be to run a current through the other substance in the opposite direction to that in the electromagnet, but that means you would just build another electromagnet out of the substance.

In short, it is not possible. But i'm not an expert and also needed to ask an electrician at work.

That is a fascinating read on a Friday morning. Also, I can imagine the electrician being like:

 

[Grildon Tundy]

If you reverse the polarity of the current in the electromagnet, the magnetic field in the electromagnet is also reversed, which repels the other substance for a very short time, but then also reverses the magnetic field in the substance, so that the electromagnet attracts the other substance again.

The only solution would be to run a current through the other substance in the opposite direction to that in the electromagnet, but that means you would just build another electromagnet out of the substance.

In short, it is not possible. But i'm not an expert and also needed to ask an electrician at work.

Thank you so much. I thought posting this question was a shot in the dark, but here we are!

 

[Grildon Tundy]

I wonder if an AC electromagnet could do it. Or a combination of 2 DC electromagnets, where one switches relative to the other. The answer is probably already in Con-Z-epT's reply but it's early, my brain is slow, and I need to revisit it later.

 

[Con-Z-epT]

Thank you so much. I thought posting this question was a shot in the dark, but here we are!

Well that's why I could gather in my brain and by talking to some colleagues. But it certainly sparked a conversation.

 

[German Hops]

I think Grildon is secretly working on a superconductor experiment.

 

[jason10mm]

Reversing polarity of the ion filters and channeling that through dilithium crystals to the deflector dish should achieve your goal..

 

[BlackTron]

It's simple really

 

[sono]

Yes the only way to repel requires two magnets (electromagnetic or otherwise) with the same poles adjacent to each other afaik

 

[Crayon]

 

[midnightAI]

 

[badblue]

 

[Grildon Tundy]

I'm thinking I'll make my own electromagnet tailored for what I want to do because something's funky with mine.

This page says I should be able to reverse the polarity by reversing the positive/negative:

Which end of an electromagnet is north?

Which end of an electromagnet is north? If the current flows in a clockwise direction then the end you are looking at is the south pole if not its the north.

mammothmemory.net

Get a ferromagnetic cylinder, wrap coils around it, power it. Then if I want to switch from attract to repel, I'd just switch the connections from positive to negative and vice versa to reverse the current.

 

[Grildon Tundy]

It, uh...didn't work lol

 

[midnightAI]

Use two electromagnets not one? Or use a magnet and a spring?

 

[sono]

referring to your quoted website (you may wish to read it - is this a wind up ? (get it ? - coil WIND UP - DOH!)

 

[Grildon Tundy]

referring to your quoted website (you may wish to read it - is this a wind up ? (get it ? - coil WIND UP - DOH!)

I'm not sure what you mean.

 

[sono]

This page says I should be able to reverse the polarity by reversing the positive/negative:

That is true. But it doesn't say it will then repel instead of attract.

I'm not sure what you mean.

Reversing the polarity of an electromagnet doesn't cause iron (which isn't a permanent magnet) to be repelled from it, it doesn't matter which way the current flows it will still attract as others have said.

If you flipped the polarity of an electromagnet next to a permanent magnet and that permanent magnet wasn't fixed to the ground, it would just spin round to align opposite poles with each other, and each time thereafter you switched polarity.

 

[Grildon Tundy]

That is true. But it doesn't say it will then repel instead of attract.


Reversing the polarity of an electromagnet doesn't cause iron (which isn't a permanent magnet) to be repelled from it, it doesn't matter which way the current flows it will still attract as others have said.

If you flipped the polarity of an electromagnet next to a permanent magnet and that permanent magnet wasn't fixed to the ground, it would just spin round to align opposite poles with each other, and each time thereafter you switched polarity.

Right, but I'm using magnets to test it. I think what's happening is the magnet I'm using to test is stronger than the force in the ferromagnetic material used in the electromagnet, so the magnet used to test is overriding the magnetic force in that ferromagnetic material in the electromagnet regardless of the electromagnet's polarity

 

[I_D]

It, uh...didn't work lol

I find it hilarious that you're smart enough to build your own electro-magnet, but ignorant enough to not understand why this won't work.

The gist of it is that the object you're trying to push/pull isn't fixed to the Earth.

The polarity of your electro-magnet doesn't matter. As soon as you turn it on, the object you're trying to push/pull will turn its poles so that it is always polar-opposite to your electro-magnet.

The only way to solve this problem would be to fix the object to the Earth, so that it cannot spin in any way whatsoever. But then, of course, you also won't be able to push/pull it.

 

[Grildon Tundy]

I find it hilarious that you're smart enough to build your own electro-magnet, but ignorant enough to not understand why this won't work.

The gist of it is that the object you're trying to push/pull isn't fixed to the Earth.

The polarity of your electro-magnet doesn't matter. As soon as you turn it on, the object you're trying to push/pull will turn its poles so that it is always polar-opposite to your electro-magnet.

The only way to solve this problem would be to fix the object to the Earth, so that it cannot spin in any way whatsoever. But then, of course, you also won't be able to push/pull it.

What you are talking about applies to ferromagnetic materials. I'm interacting an electromagnet with a magnet. Yes, ferromagnetic materials will change poles. A magnet won't. A magnet can change its physical (not magnetic) orientation, sure, but there is a time before it "corrects" and spins that they would be repulsing before flipping (not poles--it's actual physical orientation) and attracting. I'm trying to quickly change polarity of an electromagnet so that the magnet gets "pushed" up before correcting and snapping to the electromagnet.

Picture the electromagnet under a table, magnet on top. They are attracting. Quickly switch the polarity of the electromagnet, the magnet on top of the table "jumps". Then switch the polarity of the electromagnet back to snap the magnet back into place. That's what I'm trying to do.

 

[I_D]

What you are talking about applies to ferromagnetic materials. I'm interacting an electromagnet with a magnet. Yes, ferromagnetic materials will change poles. A magnet won't. A magnet can change its physical (not magnetic) orientation, sure, but there is a time before it "corrects" and spins that they would be repulsing before flipping (not poles--it's actual physical orientation) and attracting. I'm trying to quickly change polarity of an electromagnet so that the magnet gets "pushed" up before correcting and snapping to the electromagnet.

Picture the electromagnet under a table, magnet on top. They are attracting. Quickly switch the polarity of the electromagnet, the magnet on top of the table "jumps". Then switch the polarity of the electromagnet back to snap the magnet back into place. That's what I'm trying to do.

Outside of using hella-strong electro-magnets, what else would your options be?

 

[22:22:22]

Me reading this tread

 

[Con-Z-epT]

Me reading this tread

Did you never felt attracted?

 

[22:22:22]

 

[Grildon Tundy]

Outside of using hella-strong electro-magnets, what else would your options be?

I'm thinking that's the way to go. Totally open to other solutions. It's been fun experimenting so far, at least

 

[I_D]

I'm thinking that's the way to go. Totally open to other solutions. It's been fun experimenting so far, at least

At the very least, I would recommend setting up some kind of barrier so that your magnet doesn't go flying off into the distance.

Besides, surely a levitating magnet is more interesting than a launched magnet?