Re: Magnetic Field in a Flat Spiral

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Sharpe by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sccr4us-at-erols-dot-com>

Paul N., All 

NIB - Neodymium-Iron-Boron Rare Earth Magnets. 
One supplier is Edmund Scientifics in USA. Used 
them as a suppler for work, recommended. 

<http://www.scientificsonline-dot-com/>http://www.scientificsonline-dot-com/ 

Relatively inexpensive for the extreme power of these 
magnets.  Edmunds stocks various sizes and shapes 
most prevalent are rectangular or disc shaped. 
Watch the warning(s) on these magnets, they nearly 
10X more powerful then old school alnico magnets! 
They can destroy credit cards, FD's, and with higher 
power units, can remove skin from fingers/or cause 
blood blisters, when contacting magnetic steel.  Some 
units removed from old HD are so powerful they can 
not be pulled normally apart, they must be slid apart. 

Wear safety glasses, they are brittle and can shatter 
like glass.  Having a super magnet sliver in your eye 
is something I don't want to ponder...and has 
happened to other folks in the past.  Consider what 
happens in that event when you walk by a steel door 
trying to get medical assistance...enough said. 

<<Off topic shield down Terry!!!>>   :^) 

Regards 
Dave Sharpe, TCBOR 
Chesterfield, VA. USA 

Tesla list wrote: 
>
> Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <paul-at-abelian.demon.co.uk> 
>
> David Thomson wrote: 
> > NIB magnet in various positions around the coil. 
>
> That's a really neat experiment - what a nice demonstration of the 
> shape of the field around a coil, every school physics lab should 
> have some of those NIB magnets, not to mention a TC or two! 
>
> Your description of the shape of the field as determined by the 
> magnet's vibration is very clear and spot on. 
>
> Beats the heck out of iron filings any day!  Nice one. 
>
> FYI, 
> It's quite easy to plot the magnetic field around an air cored coil, 
> just apply Biot and Savart's law to lots of points in a plane 
> containing the axis of the coil.  Work in cylindrical coordinates so 
> that you only have to sum components in the r and z directions, then 
> plot a little arrow at each point.  An easy and worthwhile 
> programming exercise - an hour or two, tops.  A little more of a 
> challenge if you want to plot field lines. 
>
> BTW, what's an NIB disk magnet, and where do I get one from? 
> -- 
> Paul Nicholson 
> --