Date: Mon, 11 Apr 2011 13:17:49

Author: Zani, Gerald

Subject: Re: Jumping Ring

Post:

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Richard,

Very interesting work.
It is always great when the students become simultaneously excited and
puzzled at the same time by an experimental result. It is really the joyful
part of learning.

Actually, I was aware of those large magnitudes of the currents in an eddy
current. A Professor Lou Caldwell from PC came to my lab years ago to
measure the magnitude of the eddy currents when he was writing the following
publication, which is surprising if you read it because it indeed states
what you found, the currents are as high as 1000 Amps!:

Magnetic damping: Analysis of an eddy current brake using an airtrack
Am. J. Phys. 64, 917 (1996)

Best,
- Jerry

On Mon, Apr 11, 2011 at 12:43 PM, Richard Flarend wrote:

> Out of curiosity, I had my students calculate the current induced in the
> ring of the Pasco jumping ring apparatus. OMG, it came out at over 1300A!
> But the induced emf is only 0.05 V. This started a great discussion over
> "Why am I not killed when holding a ring carrying over 1000A?" Which then
> brings up stuff like birds on power lines. You can even hold the cut ring
> so that you are part of completing the circuit.
>
> Richard F.
>
>

--
Gerald Zani
Demonstration Manager
Physics
Brown University
(401) 863-3964

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Richard,Very interesting work. It is always great when the stud=
ents become simultaneously excited and puzzled at the same time by an exper=
imental result.=A0 It is really the joyful part of learning.Actuall=
y, I was aware of those large magnitudes of the currents in an eddy current=
.=A0 A Professor Lou Caldwell from PC came to my lab years ago to measure t=
he magnitude of the eddy currents when he was writing the following publica=
tion, which is surprising if you read it because it indeed states what you =
found, the currents are as high as 1000 Amps!:

Magnetic damping: Analysis of an eddy current brake using an airtrackLouis H. CadwellAm. J. Phys. 64, 917 (1996)Best,- JerryOn Mon, Apr 11, 2011 at 12:43 PM, Rich=
ard Flarend edu> wrote:

Out of curiosity,=
I had my students calculate the current induced in the ring of the Pasco j=
umping ring apparatus. =A0 OMG, it came out at over 1300A! =A0But the induc=
ed emf is only 0.05 V. =A0This started a great discussion over "Why am=
I not killed when holding a ring carrying over 1000A?" =A0Which then =
brings up stuff like birds on power lines. =A0You can even hold the cut rin=
g so that you are part of completing the circuit.

Richard F.

-- Gerald ZaniDemonstr=
ation ManagerPhysicsBrown University(401) 863-3964

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