# induction ?

Discussion in 'The Projects Forum' started by Mathematics!, Aug 3, 2008.

1. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
1,022
4
Ok, I was sucessful in verifying the law of induction.
I took a 1.5 volt AAA battery a screw and about 22 turns of 22gauge copper wire. It was able to pick a tiny screw. My only question is way after I did the experiment was the screw still magnitized. It was like I created a weak permanate magnet. Does this just last for a few hours or something.

If not , How do I demagnitize it. Without heating the crap out of it.
Tried rubbing it but I am really not sure what to use if anything.

Also I know you cann't magnetize copper. So if we didn't have a screw in between the coil of wire would it still make a magnetic field? I thought around any wire their is a magnetic field in the shape of circles around the wire. But with copper is their NO CIRCLES because their should exist a magnetic field around any wire that has current going thru it. So why doesn't copper have poles I thould if you have a magnetic field then you have a north pole and a south pole. No monopoles exist this can be seen by maxwells equations. Either their is no magnetic field around copper
(which isn't true ) or the force vector's cancel out some how

Could we use (instead of copper wire) iron or steal wire and wind it in coils with nothing inside it. And have it attract objects.

Thanks for any clarity.

Apr 5, 2008
19,802
4,109
Hello,

You can demagnatize it with an AC voltage.
This will destroy the magnetic propety it gained by the coil.

Greetings,
Bertus

3. ### SgtWookie Expert

Jul 17, 2007
22,201
1,809
Longer. Exactly how long is hard to say.

Here are a couple of ways:
1) Run a pole of a magnet down the screw several times. Then test it to see if the magnetic field is stronger or weaker. If it's stronger, run the opposite pole of the magnet down the screw several times.

2) Apply a steadily decreasing AC voltage to the coil, or place the screw on a transformer for a while, and then slowly pull the screw away from the transformer. The transformer may not work very well, since they're generally designed to keep the magnetic field pretty well contained.

3) Use a degausser. These are devices that are designed to remove magnetic fields from materials; CRT screens, VCR tapes, floppy disks, etc. Your television set has a degaussing coil built in. Every time you turn it on, you hear an odd noise for a moment; that's the degausser at work, removing magnetic charges from the picture tube.

Yes.
It's in the shape of a toroid; a donut if you will.
The copper kept your ferros objects too far away to be attracted to the small magnetic field you were generating. The iron or steel core serves to concentrate the magnetic field.

Iron and steel are very poor electrical conductors compared to copper.
Iron has 5.799 times the resistance than copper does, and is relatively brittle.
Steel has 9.932 times the resistance that copper does.
Stainless steel has 52.941 times the resistance that copper does.
Besides, you don't really want iron and steel objects hitting your wires and knocking bits of insulation off.