Electromagnet query

Thread Starter

salvus

Joined Apr 2, 2020
5
Hi,


I would like to attract a neodymium magnet to an electromagnet. I am wondering if I could use a small SMD inductor, this is because they are cheap and easy to integrate in my application. I think it will be a rubbish electromagnet because the turns are not that high and they are small, but the neodymium magnet is quite strong. If it was just a piece of metal I was trying to attract then I know that this wouldn't work. Would the fact that the neodymium is quite strong help the situation?

Thanks for your help and advice.
 

AlbertHall

Joined Jun 4, 2014
9,830
If the coil has a ferrite core then the magnet will be attracted to it whether or not there is a current flowing in it and that effect may be stronger than any effect the coil current has.
 

Thread Starter

salvus

Joined Apr 2, 2020
5
What if there is no ferrite core? I have seen some small coils without a ferrite core. Will the strong magnet compensate for the weak magnet?
 

KeithWalker

Joined Jul 10, 2017
889
What if there is no ferrite core? I have seen some small coils without a ferrite core. Will the strong magnet compensate for the weak magnet?
The magneto motive force of a coil is directly proportional to the current x number of turns, so how much current, how many turns and how much force are you talking about?
 

Tonyr1084

Joined Sep 24, 2015
4,517
Once took two 110 VAC coils - hollow coils and stacked them one over the other. Then powered one of the two coils and measured the voltage on the other. Got somewhere close to 110 volts but I don't recall as it's been a very very long time ago. I then connected the second coil to a 110 lamp. Powered the first coil but there was no light. Stuck a screwdriver down in the middle of the core and the light began to light up. Stuck several pieces of ferrous metals down the cores and the light began to glow full brightness (or at least what I could perceive as full brightness).

Without the iron core there's nothing to channel the magnetic power.

Cell phones have - what I call - a pancake coil. Meaning the coil is one or two winds long and dozens of layers. And I don't speak from knowledge or experience, just some things I tried a very long time ago. When the two coils are in close proximity they transfer their power. Keep in mind the magnetic flux around each wire is small. The iron core will channel the magnetic forces whereas the individual wires like to produce their own fluxes.
 

Thread Starter

salvus

Joined Apr 2, 2020
5
Hey. I don’t have exact numbers but the coil will be small and my power source will be a few AA batteries. It will undoubtably be very weak. Would the strength of the permanent magnet have an effect though? I have in mind that there would be a stronger attraction between the weak electromagnet and a strong permenant magnet, than there would be for the same electromagnet and just a piece of metal. Is that incorrect?
 

KeithWalker

Joined Jul 10, 2017
889
Hey. I don’t have exact numbers but the coil will be small and my power source will be a few AA batteries. It will undoubtably be very weak. Would the strength of the permanent magnet have an effect though? I have in mind that there would be a stronger attraction between the weak electromagnet and a strong permenant magnet, than there would be for the same electromagnet and just a piece of metal. Is that incorrect?
That would depend on the permeability of the magnetic material, the magneto motive force of the coil and the dimensions of both. There are too many variables to answer your question.
 

cmartinez

Joined Jan 17, 2007
6,953
Hey. I don’t have exact numbers but the coil will be small and my power source will be a few AA batteries. It will undoubtably be very weak. Would the strength of the permanent magnet have an effect though? I have in mind that there would be a stronger attraction between the weak electromagnet and a strong permenant magnet, than there would be for the same electromagnet and just a piece of metal. Is that incorrect?
If you were to place the magnet halfway inside the coil, believe me 'cause I've done it, the attraction or repulsion on the magnet would be very strong. That's how a bi-directional solenoid works.
 

MrChips

Joined Oct 2, 2009
21,087
Hi,


I would like to attract a neodymium magnet to an electromagnet. I am wondering if I could use a small SMD inductor, this is because they are cheap and easy to integrate in my application. I think it will be a rubbish electromagnet because the turns are not that high and they are small, but the neodymium magnet is quite strong. If it was just a piece of metal I was trying to attract then I know that this wouldn't work. Would the fact that the neodymium is quite strong help the situation?

Thanks for your help and advice.
No. It would not work. It would be like a donkey trying to pull a locomotive.
 
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