Re: Coil Winding Trouble

From: W. Watson (wolf_tracks_at_invalid.inv)
Date: 03/29/05 

Date: Tue, 29 Mar 2005 13:52:41 GMT

John Popelish wrote:

> "W. Watson" wrote:
>
>>We have an exhibit at our local science museum that is a 3-4' 1" diameter tube
>>with about 150' of wire wrapped around 8" of one end. First 75' were wound, and
>>then another 75'. An LED is connected across the wires. When a cow magnet is
>>dropped down the tube, the LED lights momentarily. Some time ago someone
>>deliberately broke the exhibit. I had to unwind the last 75' to make some
>>repairs. When I try the new configuration out, the LED doesn't light. I'm sure
>>the connections are correct. At least a continuity check at the leads shows a
>>connection. I would think if 1/2 the wire is wound the opposite way from the
>>other 1/2 that maybe no current would appear. Is that right?
>
>
> If the two halves are in series, that is correct. The wire has to all
> wrap around the magnets the same way, since each turn makes a
> contribution to the total voltage.
>
> Have you checked the LEDS to make sure they have not been damaged?
>
> By the way, another neat magnet - generated current demo is to drop a
> neodymium iron boron or samarium cobalt magnet down a copper pipe not
> much larger than the magnet. It falls very slowly because of the
> interaction with the magnetic field produced by the high currents that
> are generated around the magnet. The forces also keep the magnet away
> from the pipe. I even got this to work just rolling a cylindrical
> magnet down an aluminum flat strip. It rolled slowly, and when the
> magnet got near the edge, the drag forces dropped, that end sped up,
> and the magnet was steered away from the edge. It zig zagged all
> across the strip as it crawled to the bottom but never went over the
> side. An example of a gravity powered mechanical negative feed back
> loop.
>
I tried 5-6 LEDs. Sounds right to me. Thanks. Weather permitting, I think I'll
do the rewinding outside. I just had to check before facing the confines of my
garage again. It takes about an hour in my garage. Alice-in-Wonderland would
feel happy there.

Yes, I'm familiar with those demos. Eddie's currents. :-) I always liked that
guy. Fun stuff. 

-- 
              Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
                  (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
                   Obz Site:  39° 15' 7" N, 121° 2' 32" W, 2700 feet
             "I know that defies the law of gravity, but, you see, I never
              studied the law of gravity." -- Bugs Bunny
                         Web Page: <home.earthlink.net/~mtnviews>

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