The conductivity increases a lot with thickness. A thin-walled copper
pipe that you might use for plumbing will show no drag when you drop a
magnet through it.


On Friday, September 26, 2003, at 08:33 AM, Thomas J. Bauer wrote:

> writes:
>> Sammy, Zig, Matt, and Tappers all,
>> I also did this experiment when I was giving a colloquium
>> presentation to
>> my department last monday. I had actually obtained a 1 inch thick by
>> 1
>> foot square piece of copper and cooled it for the first time for that
>> talk. Dropped the magnet from a height of better than two feet. It
>> fell
>> to 3 inches above the plate and then bounced back up to 6 inches and
>> then
>> slowly dropped back to the plate while sliding sideways. Surprised
>> the
>> hell out of me, and I was prepared for it to bounce.
>> Kudos to Doug Osheroff for initiating the revival of this "lost" demo.
>> Dale Stille
>> U of Iowa
> Does the copper really need to be this thick? The induction current is
> not
> very deep, so in theory a piece of 1/16" or thinner sheet should work
> just
> fine, except for staying cold. I was thinking of using a 1/4" x 12" sq.
> piece for weight and $ considerations.
> Tom Bauer
> Wellesley College
From Fri Sep 26 07:14:07 2003
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