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        riddles >> easy >> Magnet Detection
        
(Message started by: Kozo Morimoto on Aug 2^nd, 2002, 6:25pm)

Title: Magnet Detection
Post by Kozo Morimoto on Aug 2^nd, 2002, 6:25pm

Trying to remember my primary school physics...

I recall drawing magnetic field line between the poles and getting weaker as it gets to the middle of the magnetic rod...

So if you hold the 2 rods in a "T" shape and the rods stick, then the bottom of the "T" is the magnet. If it doesn't do anything, then the top of the "T" is the magnet.

Title: Re: Magnet Detection
Post by Chris-Bob on Aug 19^th, 2002, 3:07pm

Alternatively, balance one on the center of the other (or on a finger, if that doesn't count as an "instrument"), and spin them as a unit. If the rod that's free to pivot does (i.e. aligns itself along the earth's magnetic field as a compass), then it's the magnet.

Title: Re: Magnet Detection
Post by jim p on Aug 23^rd, 2002, 12:50pm

Assuming they were thin enough and that you were strong enough to break the rods in half, you could easliy determine this. Take the opposite ends of the rod you broke and push them towards eachother. If you see that they oppose eachother (as the poles N and P would) that is the magnet. If not, that is the normal iron rod.

Title: Re: Magnet Detection
Post by James Fingas on Aug 30^th, 2002, 12:55pm

Jim,

Actually, that's the answer I was thinking of, but:

1) Physical shock can demagnetize magnets
2) Physical shock can spontaneously magnetize magnetic materials

So you might be left with two sort-of magnets and a lot of confusion.

Title: Re: Magnet Detection
Post by shivbits1 on Sep 24^th, 2002, 1:36pm

the rods will stick in T shape no matter what.
the field is weak in the middle of the magnet but a field still exists.
So in T shape, even if the top of the T is the magnet, they will still stick.

on 08/02/02 at 18:25:15, Kozo Morimoto wrote:

Title: Re: Magnet Detection
Post by shivbits1 on Sep 24^th, 2002, 2:49pm

ok, dealing with the demagnetization due to shock,
so lets not 'hammer' the magnets.
use a nice hacksaw and finely saw of a piece of the magnet!

on 08/30/02 at 12:55:59, James Fingas wrote:

Title: Re: Magnet Detection
Post by jeremiahsmith on Sep 24^th, 2002, 8:21pm

on 09/24/02 at 13:36:02, shivbits1 wrote:

the rods will stick in T shape no matter what.
the field is weak in the middle of the magnet but a field still exists.
So in T shape, even if the top of the T is the magnet, they will still stick.

Well, you could always check to see which T is stronger.

Title: Re: Magnet Detection
Post by Kozo Morimoto on Sep 27^th, 2002, 5:15pm

I remember doing experiments back in grade 1 trying to pick up iron filings and paper clips. You could not pick up iron filings at the middle of the rod magnet.

Maybe still using the T shape, but by sliding the bottom of the T side ways back and forth and see if the strength of the attration changes. If it doesn't, then you are holding the magnet, if it does change, then the top of the T is the magnet.

Title: Re: Magnet Detection
Post by BB on Sep 4^th, 2005, 12:31pm

Didn't anyone ever turn a piece of metal into a magnet before? Iron has a great affinity for being able to temporarily turn into a magnet.

Rub the ends of the iron rods together for a while. Usually its best to rub in one direction like honing a knife. After a while, spin one of the magnets around. If it attracts, its just a piece of iron. If it repels, its a magnet.

Title: Re: Magnet Detection
Post by Grimbal on Sep 5^th, 2005, 1:44am

on 09/04/05 at 12:31:31, BB wrote:

Rub the ends of the iron rods together for a while. Usually its best to rub in one direction like honing a knife. After a while, spin one of the magnets around. If it attracts, its just a piece of iron. If it repels, its a magnet.

I'm not convinced.
If you are rubbing the 2 pieces of metal, and one of them is a magnet, the other will magnetize. Assuming the magnetization is strong enough, regardless of which was the neutral iron, they will repel.

About another suggestion to saw the bar in 2, as soon as you have a little metal dust, you can tell easily which of the bars is the magnet.

Title: Re: Magnet Detection
Post by towr on Sep 5^th, 2005, 2:53am

on 09/05/05 at 01:44:39, Grimbal wrote:

Only if the entire bar of iron is magnetized, it's much more likely it will only be magnetic at one end, I think.

Title: Re: Magnet Detection
Post by rmsgrey on Sep 5^th, 2005, 6:02am

on 09/05/05 at 02:53:06, towr wrote:

Only if the entire bar of iron is magnetized, it's much more likely it will only be magnetic at one end, I think.

But iron in contact with a magnet tends to act like a magnet - anyone who's ever played with steel paperclips and a magnet will know that,aslong as you keep the chain unbroken, you can pick up a lot of paperclips - break the chain in the middle, and the portion not connected to the magnet will fall apart.

Title: Re: Magnet Detection
Post by towr on Sep 5^th, 2005, 12:49pm

on 09/05/05 at 06:02:03, rmsgrey wrote:

But the chain can only go so long, even when you don't hang the chain (which would increase the force)
So i suppose it depends on the size of the bar..

Title: Re: Magnet Detection
Post by Justin on Dec 14^th, 2005, 4:01pm

on 09/24/02 at 14:49:34, shivbits1 wrote:

ok, dealing with the demagnetization due to shock,
so lets not 'hammer' the magnets.
use a nice hacksaw and finely saw of a piece of the magnet!

You're not allowed to use any other instruments!