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Re: [Phys-L] breaking magnets



Makes sense. Thanks for the clarification. When my grades are in, I'll go try the experiment! :-)

KC

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of John Clement
Sent: Sunday, 4 May, 2014 4:46 PM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] breaking magnets

I left out of the experiment the fact that you can use a pencil to prevent the magnets from slipping. The effect is more pronounced when you try testing opposing magnets. The effect for magnets the same direction is not 2x because of the drop off of the dipole field. The lower magnet does not have as much effect on the floating test magnet as the the top magnet. This experiment can be done easily by students.

As to the bar magnets, if the original magnet is fairly long the change in strength of breaking it will not be very noticeable. But in the limit of disc magnets breaking it into 2 pieces shouls be noticeable. The very near field of course is not affected as much. The disc magnet experiment is useful for getting students to think about how magnets work. Side by side bar magnets aligned the same way do have noticeably greater strength. Once students see their misconceptions refuted, the model of magnets having "nanomagnets" inside them is very reasonable. The big idea is nanomagnets, and the domain structure is just a refinement. The nanomagnet model can be used to explain quite a lot of phenomena without going into the idea of domains.

I did not invent this experiment, as it is a standard thinking activity from Minds-on-Physics. I just refined the testing to help the students see the effect after they have come up with predictions.

John M. Clement
Houston, TX

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of Ken
Caviness
Sent: Sunday, May 04, 2014 3:28 PM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] breaking magnets

Ok, that's a lower bound. But is the force at any given distance
provided by the combination of 2 disc magnets on some object = twice
the force of one disc magnet at the same distance on the same object?
Or is it greater/less than twice the force of one disc magnet? My
quick and dirty model says "=", but "slightly greater" wouldn't
surprise me.

KC suspects that the JC's answer wasn't actually what the questioner
was asking.

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of John
Clement
Sent: Sunday, 4 May, 2014 2:02 PM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] breaking magnets

If you put together 2 disc magnets, the resulting magnet is stronger
than either individually. This is easy to test if they have a hole in
the middle and you put a magnet opposing them on the top.

John M. Clement
Houston, TX

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of Larry
Smith
Sent: Monday, April 28, 2014 12:28 PM
To: Phys-L@Phys-L.org
Subject: [Phys-L] breaking magnets

If you break a simple dipole bar magnet in two unequal pieces, how
does the strength of the pieces relate to the strength of the
original?

Larry


_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l

_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l
_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l

_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l