Date: Fri, 26 Sep 2003 13:18:10 -0400

Author: Wolfgang Rueckner

Subject: Re: Awesome EM induction demo!

Post:

I use a 6"x6"x2" and it works great. As I posted this summer to
tap-l, the difference between oxygen free and regular copper is not
noticeable, even at LN2 temps. I've tried different rare-earth
magnets and found a huge difference between them. A supplier's
comment like "The most powerful magnet on earth...." is not that
meaningful. Wolfgang



>Hi Wolfgang,
>thanks for the info. The magnet I tried that worked best was really
>hard to pull off a blackboard. It was sold to be by Arbor Scientific
>as "The most powerful magnet on earth...." so I've got to wonder if
>it's really the problem. I'm wondering if 6 inch by 6 inch is too
>small an area, I wonder if anyone else has had success with this
>sized plate, perhaps it's the "oxygen free" that matters,
>cheers,
>David
>
>Wolfgang Rueckner wrote:
>
>>Hi folks,
>>I recently purchased a 6 inch by 6 inch by 2 inch thick piece of copper,
>>cooled it down to ln2 temp. and dropped a 1 inch diameter neodymium magnet
>>onto it. I only got a 7 inch drop, any more and the magnet hit the copper.
>>It's just commercial copper block, cost me $100. I have been reading the
>>discussion on this but may well have missed something. It's not been
>>"degassed" or anything, any idea what am I doing wrong here folks? I've got
>>a bad case of envy here, size does matter cheers,
>>David
>
>
>>Your problem is very likely the magnet and not the copper. Some
>>NIBs are stronger than others and work better. Wolfgang
From rueckner@fas.harvard.edu Fri Sep 26 10:37:12 2003
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