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Q & A: temporary magnet

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Most recent answer: 04/01/2013
Q:
Hi =) I know that you have answered several questions on how to make a permanant magnet. But would you be able to tell me how to make a temporary magnet?? The kind that when you turn on the battery, it becomes a magnet, and when you turn it off, it no longer is one?? And where I can find materials?? It is for a science project and I have no clue where to start. Thanx
- stephen (age 15)
upstate New York
A:
This one is easy. Just make a coil of many turns of wire. When current flows through it, it's a magnet. A small battery can be used to supply the electrical current. You may want a variable resistor in series to control the amount of current and to keep the battery from wearing out too fast. To make your temporary magnet stronger, you can wrap the coils around a piece of iron or steel. But you will probably end up magnetizing the iron, thus making a permanent magnet in the process. You can find all this stuff at an electronics supply shop, or even a hardware store.

Mike W. (and Tom)

(published on 10/22/2007)

Follow-Up #1: electromagnet pictures

Q:
SHOW ME SOME DIGRAMS demonstrating how to make a temporary magnet
- SSERUGO HUZAIFA (age 14)
UGANDA BWEYOGERERE
A:
  See: 

(published on 08/26/2009)

Follow-Up #2: magnet wire

Q:
Why should we use only an insulated wire to make an electromagnet.Cant we use directly a wire which is made of a conductor?
- Prudhvi Raj Borra (age 16)
Machilipatnam,Andhra,India
A:
Sure, the wire itself must be a conductor. The insulation just wraps around the wire, so that the current has to flow through the wire instead of leaking from one wire over to the one next to it.

Mike W.

(published on 08/30/2009)

Follow-Up #3: re-entrant ferromagnets

Q:
I would like to know if there is a material like hemitite that can be magnetized temporally when heat is applied,and demagnetized when cooled.
- larry fealy (age 77)
apple valley, ca. san bernardino ct.
A:
It sounds like what you're looking for is what's called a "re-entrant ferromagnet", something that goes from a less magnetic state to a ferromagnetic state when it's warmed. (It'll then leave the ferromagnetic state if warmed too much.) Some of the materials called re-entrant ferromagnets go to combined ferromagnet-spinglass states when cooled, but that's not what you want. You want the cool state to be paramagnetic or antiferromagnetic. Here's a paper on one such material, SmMn2Ge2:
  .

Mike W.

(published on 04/01/2013)

Follow-up on this answer.