Electromagnet attracting non-ferrous metals

[iceworm]

Has anybody done any work with electromagnets attracting non-ferrous metals? One of the kids in the neighborhood is asking about how one would do this. She wants to do a science fair project on this.

I've heard of the concept. But my understanding of the physics is dim. It's not something that comes up in engineering school or anything I have ever had to work on.:?

Mostly I am looking for some references to get me started. Judging from previous years projects, my part of this will be to get her aimed in the right direction for the research. Oh yeah, I'll need to learn enough to answer the questions that I'm sure will be coming.

She has a 1951 pamphlet from Universial Scientific Company, it doesn't give enough of the physics to do the calculations.

I'm off to work Monday, but I'll be able to check in next week. Any help will be graciously appreciated.

ice

 

[mivey]

Eddy currents. You can make an aluminum plate stick to an electromagnet.

Not sure if that is what you are referencing.

 

[Sierrasparky]

Eddy currents. You can make an aluminum plate stick to an electromagnet.

Not sure if that is what you are referencing.

Never knew that!

 

[mivey]

Never knew that!

Favorite trick of EE professors to suprise the class and make them think.

Here is a commercial unit:
http://www.google.com/url?sa=t&rct=...__29DQ&usg=AFQjCNGe1YMuHenbsLWgZu8Zo3IisxOHXw

and here
http://www.steinertus.com/Overviews/superior-separation.html

Couple of Google links:
http://www.lindsaybks.com/bks2/elmag/index.html

http://www.rexresearch.com/mrmagnet/mrmagnet.htm

 

[iceworm]

Couple of Google links:
http://www.lindsaybks.com/bks2/elmag/index.html

http://www.rexresearch.com/mrmagnet/mrmagnet.htm

Thanks for looking that up.

The first is a page out of the 1951 pamphlet Although the one I read looks like a fugitive from the Korean War. Hummm ... I guess it probably is.

We also have the second. It is a pretty good construction article. Not much on the physics though.

Keep 'em coming. I appreciate it.

ice

 

[jim dungar]

Eddy currents are behind the operation of the spinning aluminum plate in a standard KWHR meter.

 

[John120/240]

Nickel a non ferrous metal, has magnetic properties. How's it do that ? I don't know. In large junkyards they

have cranes fitted with magnets. Iceworm might inquire at one.

 

[K8MHZ]

Eddy currents. You can make an aluminum plate stick to an electromagnet.

Not sure if that is what you are referencing.

Aluminum is paramagnetic. So is Platinum and Oxygen. No eddy currents needed in a strong field. Eddy currents also affect copper. In fact, eddy currents will affect anything that conducts electricity. The force of attraction from eddy currents is different than the force of magnetism.

Copper is diamagnetic, it is in the same category as glass and plastic. It is repelled from both poles of a magnet.

Check out this 'magic trick' where copper seems to attract a magnet. It's a fun and easy experiment.

http://www.grand-illusions.com/acatalog/Lenz_s_Law_Demo.html

 

[K8MHZ]

Nickel a non ferrous metal, has magnetic properties. How's it do that ? I don't know. In large junkyards they

have cranes fitted with magnets. Iceworm might inquire at one.

Iron, nickel and cobalt are all attracted to magnets.

 

[kwired]

Iron, nickel and cobalt are all attracted to magnets.

Women are attracted to gold and diamonds

 

[jjkind]

Has anyone ever tried this or have video of someone picking up something other than foil? The relative permeability of aluminum is almost 1, basically it is as magnetically impermeable as air, so your field isn't going to penetrate the aluminum very much (to induce your eddy currents).

I'm assuming that your magnetic field has to be switching to get it to work?

 

[mivey]

Has anyone ever tried this or have video of someone picking up something other than foil?

No video, but in our lab the sheet of aluminum was about 4" square and probably 1/16"-1/8" thick. But that's testing some pretty old memory cells.

 

[iceworm]

Eddy currents. You can make an aluminum plate stick to an electromagnet.

Not sure if that is what you are referencing.

Close. Here is my current understanding of the physics (pun intended):
To get non-ferrous material to stick to an electromagnet one has to trick (direct the path) the electromagnet field a bit.

Basic principal is a consequence of Lentz's Law.

Place a copper washer (or any other non-ferrous conductive material) on the face of an AC electromagnet and then energize the magnet. The washer is repelled from the face of the magnet. The changing magnetic field through the washer induces a current around the washer. The induced current sets up a magnetic field around the washer. This field is in opposite direction of the electromagnet field. So, the mag field around the washer is repelled by the electromagnet field. And the washer is pushed away form the electromagnet.

This is the Lentz's Law part.


Now, put two copper washers on the face of the electromagnet. Both get a current induced, both get a magnetic field from the induced current. Both are repelled from the electromagnet. BUT, since the magnetic field around the two washers is the same direction, the two washers are attracted to each other.

Now, fasten the first washer to the electromagnet so it can not move. Now, the second washer is attracted to the first washer with more force than it is repelled from the electromagnet.

This also works with a flate plate for a second washer. However, the physics is a bit easier for me to see using washers.

Jump in here and straighten out my understanding. It's okay to get pretty basic. I don't have a clear understanding of permeability yet - working on that. References will of course be will be graciously appreciated. I don't mind doing my own reading.

ice (Working but will check back later)

 

[iceworm]

Bummer -

I was hoping there was some collective knowledge

Thanks anyway.

I'm out for a month or so - later

ice

 

[Besoeker]

Rare earth magnets are non-ferrous.
Samarium cobalt is one example.

 

[mivey]

I was hoping there was some collective knowledge

Don't really know what else to add. Maybe a video?:
http://www.wisc-online.com/ViewObject.aspx?ID=ACE13207

 

[K8MHZ]

Don't really know what else to add. Maybe a video?:
http://www.wisc-online.com/ViewObject.aspx?ID=ACE13207

How about some info on magnet safety?

From Wiki:

The greater force exerted by rare earth magnets creates hazards that are not seen with other types of magnet. Neodymium magnets larger than a few centimeters are strong enough to cause injuries to body parts pinched between two magnets, or a magnet and a metal surface, even causing broken bones.[4] If one accidentally becomes pinched between two magnets, or between a magnet and some magnetic material, such as steel, the natural reaction is to pull free. However, doing so makes the space between the magnets become thinner, and the pinch force increases dangerously. If possible, one should bear the pain and do whatever one can to keep the distance from closing up; only then should one pull free. Professionals who work with such magnets might include brass wedges as part of their tools.

 

[don_resqcapt19]

Another issue with rare earth magnets is that they are very brittle and can shatter if you let them come together from any distance. Safety glasses are a must if you are playing with them.

 

[SAC]

If interested in the subject, this looks like it might be worth investigating (regardless of the dubious domain):

http://www.free-energy-info.com/Non-Ferrous-Magnet.pdf

 

[jdcpe17]

man, how strong a magnet did you use to pick up the al foil?