Re: Magnetic Field in a Flat Spiral

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

Original poster: "Peter Lawrence by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>

Guys,
     just be sure you understand that a permanent magnet in an oscillating
B field will vibrate from
	a) dipole misalignment -the magnet will vibrate rotationally
	b) dipole aligned - the magnet will vibrate longitudinally
also remember that if there is no spacial gradient to the B field the magnet
will only feel the dipole misalignment rotational force (fortunately B
fields with no spacial gradient are very rare, certainly not found around
flat spiral primaries).

-Peter Lawrence.


>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
>--
>
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