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-   -   Closed loop vs open loop resistance magnet drop demo (http://www.physicsforums.com/showthread.php?t=490590)

 Robin Hooper Apr15-11 12:55 PM

Closed loop vs open loop resistance magnet drop demo

Hello everyone, curious about something here.

I saw a demonstration lately were a magnet was dropped down a copper pipe and the magnet dropped very much slower than expected. What I got to thinking was, if you replaced the copper pipe with the same quantity of insulated copper wire in a closed loop configuration and compared the fall rate to an open loop setup. Would the magnet fall slower in a closed loop than the open loop setup? My intuition would say that the closed loop coil would farther reduce the fall rate because you now have electron flow(current) which would setup its own magnetic field adding to the resistance of the copper wire.

Thanks

 skeptic2 Apr15-11 06:41 PM

Re: Closed loop vs open loop resistance magnet drop demo

Did anyone offer an explanation of why the magnet fell slower in the copper tube. Do you have any idea? What is your guess about why an open loop or closed loop may affect the magnet differently?

 Robin Hooper Apr16-11 03:02 AM

Re: Closed loop vs open loop resistance magnet drop demo

Quote:
 Quote by skeptic2 (Post 3248961) Did anyone offer an explanation of why the magnet fell slower in the copper tube. Do you have any idea? What is your guess about why an open loop or closed loop may affect the magnet differently?
No, I was just a passer by, I had no oppertunity to ask. I understand that the magnetic field behaves much like when you run your open hand though water, there is a resistance felt. An open loop would be very much like the copper tube, magnetic field going through copper. I suspect that a closed loop would setup an opposing current futher reducing the fall rate in addition to the magnet moving through the copper, but that would just be a guess.

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