Science of Magnets

[Jerry Bruette]

I was reading in the Lee Valley catalog that setting magnets into cups increases their holding power. What's the science behind this? Is it because you're increasing the surface area or some other magical reason?

[Steven Cooper2]

The little metal bit around the magnet redirects the flux and allows it to reach maybe twice the strength as otherwise.
It's kinda magic.

[Bill Dufour]

Iron cup, not wood or plastic.
Bill D

[Jerry Bruette]

Iron cup, not wood or plastic.
Bill D

Ironwood won't work?

[Bruce Wrenn]

Bought some RE magnets and cups from Lee Valley years ago. They suggested filing a notch in one side of the cup, so you could pry the magnet out if needed.

[Lee Schierer]

The little metal bit around the magnet redirects the flux and allows it to reach maybe twice the strength as otherwise.
It's kinda magic.

The iron cup concentrates the magnetic flux making the holding power increase. No magic is involved, just science.

[Ken Fitzgerald]

The iron cup concentrates the magnetic flux making the holding power increase. No magic is involved, just science.

And then there is mhu metal.

[Larry Frank]

Mu metal..high nickel metal used for magnetic shieldimg. I had to look it up on Wikipedia.

[Kent A Bathurst]

Ironwood won't work?

Drop the mic and walk away, Jerry

I laughed out loud. Well done.

[Jim Dwight]

When a magnet is close enough to a piece of ferromagnetic material, the magnetic field of the magnet causes at least some of the atoms of the ferromagnetic material to align with the field of the magnet. The steel cup becomes magnetized. Normally the steel cup would have atoms arranged randomly. So you then have the original permanent magnet plus a temporarily magnetic cup. The magnetic properties of the cup are not permanent but will be present for awhile even if the magnet is removed.

[Bill Dufour]

If you work around high power magnets all iron stuff will get magnetized. My father always ha a small screwdriver and pocket scale in his shirt pocket. They were both magnetic from his job running a cyclotron. It had over 2,000 horsepower just for the steering magnets. Not including the main drive ones. I believe it had its own 12 KV switch yard to supply incoming power..
Used special bronze wrenches and hammers. He said you could not swing a iron hammer in a straight blow. Welders hated working on it. Even gas welders had issues.
BilL D

[Alan Lightstone]

If you work around high power magnets all iron stuff will get magnetized. My father always ha a small screwdriver and pocket scale in his shirt pocket. They were both magnetic from his job running a cyclotron. It had over 2,000 horsepower just for the steering magnets. Not including the main drive ones. I believe it had its own 12 KV switch yard to supply incoming power..
Used special bronze wrenches and hammers. He said you could not swing a iron hammer in a straight blow. Welders hated working on it. Even gas welders had issues.
BilL D

Did screwdrivers fly towards your father when he walked in your shop?

[Dave Fitzgerald]

Did screwdrivers fly towards your father when he walked in your shop?

Reminds me of a story I heard when high-field NMR was a new thing. (NMR is a lab tool for chemical analysis that uses rf signals in a magnetic field; it's the technology behind MRI scanners.) The machines have liquid nitrogen-cooled electromagnets, typically decorated with signs warning users to keep metal objects away. A maintenance worker came in one night and didn't heed the signage. He was found the next morning, unhurt but unhappy, attached by his tool belt to the casing of the magnet.

[Derek Meyer]

Back in the late 90's I worked at a computer store, and a few of the techs discovered rare earth magnets. I ordered a bunch of them (20 I think) and they came stacked together. They were about 3/4" x 1" x 1/4" or so. We were playing with them, marveling about how strong they were, and someone took the whole stack and walked past my workstation, close to my monitor, which was a 19" tube monitor. The magnets were so strong that they actually grabbed the shadow mask under the monitor's glass and pulled it out of adjustment. From then on, the screen had a moire pattern all the time, looking like it was slightly out of focus. Needless to say, we kept those magnets away from screens from then on.

[mike calabrese]

If you want to experience some very powerful pound for pound magnets tear open an old computer hard drive. in the pivot structure of the disc reader arm you will find some kidney shaped magnets about 3/4 long by 1/2 wide and 1/8 thick. Stick two of them together and try to pull them apart. Even stick one to your table saw cast iron top and try to lift it.
the power in this small form it amazing.
calabrese55