How Permanent Magnet is Made

Xidike

My Question is same as the title of this thread.. and Secondly..
what is the difference between electromagnet and magnet??

Drakkith

Take a piece of magnetic material, put it in a magnetic field. It should hold its magnetic field once removed.

An electromagnetic uses electric current through a coil to produce its magnetic field. A permanent magnet does not.

sophiecentaur

I think that makes it sound a bit too simple. If you want a 'good' permanent magnet then you need a material that will 'hold it's magnetism' (good 'remnance') once it has been formed. Steel (not stainless) is a good start, although fancy ceramics are better. You then need to use a strong electromagnet (damned great piece of iron 'horseshoe shape' with a small gap between the poles). There are loads of coils of wire wrapped round it and there needs to be loads of current flowing. You turn on the current, having placed your piece of steel in the gap, there's a 'gnurrrr' as the electromagnet is activated. You turn off the current and your piece of steel is then left magnetised.
Alternatively, you can use the 'stroking' method (see all kid's textbooks) which can magnetise a steel screwdriver by stroking it with a strongish permanent magnet. This will magnetise the screwdriver enough to pick up pins and iron filings but not much more.

Railway lines become magnetised weakly by the Earth's field as they are bashed by the trains going over them.

Drakkith

Yeah, I was on my phone at lunch and couldn't really elaborate. I meant to come back to this thread when I got home.

sophiecentaur

I thought it was a bit 'terse' for you. ;-)

Drakkith

Better than being 'Tense'!

phinds

And WAY better than being past-tense

Khashishi

An electromagnet is a coil of wire, where a magnetic field appears when electricity is run through the wire. The electromagnet only acts like a magnet as long as there is a current in the wire, so it needs to be connected to some kind of power source.

A permanent magnet doesn't need an external power source. Permanent magnets have a current that doesn't go away. The current comes from alignment of spins of the electrons (and to a much smaller extent, nucleons). In some materials, at sufficiently low temperatures, the spins of the "free" electrons spontaneously align themselves so that they all point the same way. This creates a magnetic domain. If the magnetic domains are large enough, the material is "magnetized" and behaves as a permanent magnet.
You should check out https://en.wikipedia.org/wiki/Ferromagnetism
Obviously, I glossed over a lot of detail. You should study up on quantum mechanics and atomic physics.

Drakkith

Just to be clear, permanent magnets do not have current flowing through them.

Xidike

what is mean by magnetic material ??? Is iron a magnetic material ?? and what about copper ??

davenn

yes iron is as are a number of other metals

copper -- no

do a google search on rare earth elements for magnets

Dave

Khashishi

The magnetization can be represented as being due to a bound current. Charge doesn't actually flow through the material, but there is a net current along a loop around the edge of the magnetic domain. Maxwell's laws requires there to be a current, though I'm not sure how one could demonstrate that it is indeed a real current.

Xidike

Can a copper wire act like a magnet when current is passing through it ????

jtbell

Or too tense:

http://www.physicsforums.com/showthr...81#post2329281

Buckleymanor

You can make a permanent magnet by heating a rod of iron till it's red hot.
Then you put the hot iron on an anvil with the ends of the rod pointing north and south and bash it along it's length with a hammer.
So I have been told.

Xidike

Can we make a permanent magnet at our home ???

Xidike

And how to make an electromagnet ?? which type of current (AC or DC) should be passing through the wire to make it magnetize ??? Or it doesn't matter ??