physics question #2113



Fran Barnes, a 55 year old female from Kooskia, ID asks on May 31, 2004,

Q:

I have spent 4-5 hrs. attempting to magnetize some iron (Fe) washers using a 12V battery and insulated Cu++ wire coiled around them in every manner. Nothing. I read James Livingston's Q & A on magnets who spoke of using some capacitor. Can I make a capacitor in my garage? Can you please provide me with a home made step-by-step prodedure to magnetize some small round iron washers?

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the answer

Rick Hoadley, Electric Motor Engineer, Rockwell Automation answered on June 9, 2004, A:

The problem you have discovered is why so much research has gone into finding materials that retain a large amount of magnetism. Steel washers are not the best thing to magnetize. Steel of any kind can only be magnetized very slightly. There are not many metals that can become strong permanent magnets except for Alnico (an alloy of aluminum, nickel, cobalt and iron), Neodymium-Iron-Boron (a sintered mix of neodymium, iron and boron) and a few other special alloys. These are the materials permanent magnets are made from. To magnetize them, you need to generate short, 1000 to 5000 Amp pulses of current in coils that will magnetize the object, probably not something you want to try at home.

Steel does retain a small amount of magnetism, but usually not enough to pick up heavy objects. However, it is possible to magnetize screwdrivers so they can pick up and hold small screws.  Perhaps the vanadium used in the steel for screwdrivers helps them retain more magnetization. Alternatively, you can magnetize a needle enough to allow it to be used as a compass (floating on a cork in water).

To magnetize a screwdriver, wind 50 turns of #24 AWG to #16 AWG insulated wire around the steel shaft.  Connect one end of the wire to the negative terminal of a 6 volt battery.  Momentarily touch the other end of the wire to the positive terminal of the battery.  There will be a spark!  The screwdriver should now be able to pick up a screw.

If you need shapes, like washers, that are actually permanent magnets, then I suggest you purchase some donut magnets, sometimes called ring magnets.  You can obtain them with a North pole on the face (with a hole in the center of it), or it can be magnetized with a North pole on its outside edge, and South on its inside edge, or even with the North pole at one spot on its outside edge, and its South pole also on its outside edge 180 degrees around from the North pole.  So, there are several possibilities. Visit Rare Earth Magnets to get what you need.  They come in different outside diameters, with different diameters of holes in their center. Or try Amazing Magnets. You can find lots of experiments for magnets at my Magnet Man website.

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