Date: Thu, 25 Sep 2003 15:30:17 -0500

Author: "Matt Lowry"

Subject: Re: Awesome EM induction demo!

Post:

Thanks for pointing that out Zig. I had noticed a couple of nicks in
the Cu already...

So, let me extend my question: could I coat the Cu with anything to
provide it better protection?

Cheers - Matt

>>> peacock@physics.utah.edu 9/25/2003 3:15:40 PM >>>
Matt, the copper is very softer and dings up, not the magnet. Zig

Matt Lowry wrote:

> Howdy tappers,
>
> I just got my hands on the materials for the amazing demo that Zig
and
> the PIRA Gang displayed at the AAPT meeting in Madison... the alloy
101
> O2-free copper plate with neodynium magnet. It's a freakshow! My
> department is going nuts over this demo.
>
> For those who don't know, what you do is take the magnet in your
hand,
> pass it over the plate, and you can really feel the magnetic braking
> forces as a result of the EM-induction in the copper. There are all
> kinds of tricks to do with this one, but the best are with LN2
cooling
> down the copper! I strongly encourage you to check this one out.
>
> Anyway, on to my question: I'm concerned that dropping the magnet
onto
> the plate could chip it since neodynium magnets are somewhat ceramic
in
> nature. Is there anything someone would suggest that I coat the
magnet
> with in order to protect it?
>
> Cheers,
>
> Matt Lowry
> Lake Forest HS
> Lake Forest, IL

--
Zigmund J. Peacock
www.physics.utah.edu/people/staff/peacock.html

University of Utah/Physics peacock@physics.utah.edu
115 SOUTH 1400 EAST #201 Tel 801 581 6602
SALT LAKE CITY UT 84112-0830 Fax 801 581 4801

"We sleep safely in our beds because rough men stand ready in
the night to do violence to those who would do us harm"
-- George Orwell

"All that is necessary for the triumph of evil is that good
men do nothing!"
-- Edmund Burke
From gary@phys.columbia.edu Thu Sep 25 13:48:40 2003
Date: Thu, 25 Sep 2003 16:04:09 -0400 (EDT)
From: Gary Steinberg
To: tap-l@listproc.appstate.edu
Subject: Motion of falling bodies demo
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I'm trying to recreate an old demo that was used in the 60's that
is similar to Meiners 7-1.15 (page 115). Basically its an apparatus that
drops balls at a set rate in synchronization with a strobe. The main
difficulty is the dispenser--does anyone know of any industrial or
consumer products that can dispense regular objects at a set rate? Or
will this have to be custom made...

Gary Steinberg
From sampere@physics.syr.edu Thu Sep 25 13:57:34 2003
Message-ID: <3F7352A9.7050207@physics.syr.edu>
Date: Thu, 25 Sep 2003 16:40:09 -0400
From: sampere
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Subject: Re: Awesome EM induction demo!
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You're right. NdFeB magnets are very brittle and chip easily. I
haven't tried this yet, but you can get vinyl dip at Home Depot. Try
painting that on your magnets. I just painted some on lead bricks.

Sam

Matt Lowry wrote:

>Howdy tappers,
>
>I just got my hands on the materials for the amazing demo that Zig and
>the PIRA Gang displayed at the AAPT meeting in Madison... the alloy 101
>O2-free copper plate with neodynium magnet. It's a freakshow! My
>department is going nuts over this demo.
>
>For those who don't know, what you do is take the magnet in your hand,
>pass it over the plate, and you can really feel the magnetic braking
>forces as a result of the EM-induction in the copper. There are all
>kinds of tricks to do with this one, but the best are with LN2 cooling
>down the copper! I strongly encourage you to check this one out.
>
>Anyway, on to my question: I'm concerned that dropping the magnet onto
>the plate could chip it since neodynium magnets are somewhat ceramic in
>nature. Is there anything someone would suggest that I coat the magnet
>with in order to protect it?
>
>Cheers,
>
>Matt Lowry
>Lake Forest HS
>Lake Forest, IL
>
>
From wonnell@pha.jhu.edu Thu Sep 25 14:03:21 2003
Date: Thu, 25 Sep 2003 16:46:46 -0400 (EDT)
From: Steve Wonnell
To: tap-l@listproc.appstate.edu
cc: Steve Wonnell
Subject: Re: Awesome EM induction demo!
In-Reply-To: <3F734CEC.1FD2FD16@physics.utah.edu>
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Guys and Gals,

These NeFeB magnets are under extremely high internal stress.
I have a bunch of them that have cracked during storage.

I suspect that they crack far more easily than other materials (e.g.
steel, or even some ceramics).

I place a hollow acrylic tube on top of the copper plate,
and drop the magnet down this tube to guide the magnet
and protect the presenter and audience from flying fragments.

Steve








On Thu, 25 Sep 2003, Zigmund J. Peacock wrote:

> Date: Thu, 25 Sep 2003 14:15:40 -0600
> From: Zigmund J. Peacock
> Reply-To: tap-l@listproc.appstate.edu
> To: tap-l@listproc.appstate.edu
> Subject: Re: Awesome EM induction demo!
>
> Matt, the copper is very softer and dings up, not the magnet. Zig
>
> Matt Lowry wrote:
>
> > Howdy tappers,
> >
> > I just got my hands on the materials for the amazing demo that Zig and
> > the PIRA Gang displayed at the AAPT meeting in Madison... the alloy 101
> > O2-free copper plate with neodynium magnet. It's a freakshow! My
> > department is going nuts over this demo.
> >
> > For those who don't know, what you do is take the magnet in your hand,
> > pass it over the plate, and you can really feel the magnetic braking
> > forces as a result of the EM-induction in the copper. There are all
> > kinds of tricks to do with this one, but the best are with LN2 cooling
> > down the copper! I strongly encourage you to check this one out.
> >
> > Anyway, on to my question: I'm concerned that dropping the magnet onto
> > the plate could chip it since neodynium magnets are somewhat ceramic in
> > nature. Is there anything someone would suggest that I coat the magnet
> > with in order to protect it?
> >
> > Cheers,
> >
> > Matt Lowry
> > Lake Forest HS
> > Lake Forest, IL
>
> --
> Zigmund J. Peacock WWW.physics.utah.edu/people/staff/peacock.html
>
> University of Utah/Physics peacock@physics.utah.edu
> 115 SOUTH 1400 EAST #201 Tel 801 581 6602
> SALT LAKE CITY UT 84112-0830 Fax 801 581 4801
>
> "We sleep safely in our beds because rough men stand ready in
> the night to do violence to those who would do us harm"
> -- George Orwell
>
> "All that is necessary for the triumph of evil is that good
> men do nothing!"
> -- Edmund Burke
>
>


************************************************************************
Steven K. Wonnell
Physics and Astronomy Department E-Mail: wonnell@pha.jhu.edu
Johns Hopkins University Phone: (410) 516-4696, 516-5468
3400 N. Charles Street Fax: (410) 516-7239
Baltimore, MD 21218-2686 Office: 478 Bloomberg
************************************************************************
From dwilley+@pitt.edu Thu Sep 25 14:07:56 2003
Date: Thu, 25 Sep 2003 16:50:34 -0400
From: David Willey
Subject: Re: Awesome EM induction demo!
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same plastic as you'd dip tool handles in to protect them

Matt Lowry wrote:

>.....I'm concerned that dropping the magnet onto
>the plate could chip it since neodynium magnets are somewhat ceramic in
>nature. Is there anything someone would suggest that I coat the magnet
>with in order to protect it?
>
>
>
From sampere@physics.syr.edu Thu Sep 25 14:11:54 2003
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Date: Thu, 25 Sep 2003 16:55:07 -0400
From: sampere
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How about placing a 1/16" thick piece of Lexan on top of the Cu? If you
really want to coat this with something, I think coating the magnet is
the better idea. The coating has to stand up to the stress caused from
the differences in thermal expansion between the Cu and the coating.

Sam

Matt Lowry wrote:

>Thanks for pointing that out Zig. I had noticed a couple of nicks in
>the Cu already...
>
>So, let me extend my question: could I coat the Cu with anything to
>provide it better protection?
>
>Cheers - Matt
>
>
>
>>>>peacock@physics.utah.edu 9/25/2003 3:15:40 PM >>>
>>>>
>>>>
>Matt, the copper is very softer and dings up, not the magnet. Zig
>
>
>
>

--------------070404000407030403050206
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How about placing a 1/16" thick piece of Lexan on top of the Cu?  If
you really want to coat this with something, I think coating the magnet
is the better idea.  The coating has to stand up to the stress caused
from the differences in thermal expansion between the Cu and the
coating. 



Sam



Matt Lowry wrote:


Thanks for pointing that out Zig.  I had noticed a couple of nicks in
the Cu already...

So, let me extend my question: could I coat the Cu with anything to
provide it better protection?

Cheers - Matt





peacock@physics.utah.edu 9/25/2003 3:15:40 PM >>>




Matt, the copper is very softer and dings up, not the magnet. Zig








--------------070404000407030403050206--
From dstille@newton.physics.uiowa.edu Thu Sep 25 14:29:51 2003
Date: Thu, 25 Sep 2003 16:13:15 -0500 (CDT)
From: Dale Stille
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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
From dcjohnson@csupomona.edu Thu Sep 25 14:59:36 2003
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