Re: Bar magnets

[brian whatcott <inet@INTELLISYS.NET>]

At 09:58 2/19/01 -0600, Tim Folkerts wrote:
> > The question has been asked about the Coulomb balance and whether this is
> > always used with repelling charges.
>
> > I believe the answer to this is yes.  ...  If it is weak enough to allow
> > sufficient sensitivity for a meaningful measurement, you simply
> > cannot attain a stable equilibrium.
>
> But isn't this just the same as the Cavendish Balance, with electrical
> instead of gravitational forces?  It is certainly possible to do the
> gravitational attractive force, so the electrostatic attractive force
> should also be doable in principle.
>
> Tim Folkerts
> FHSU Physics

Cavendish chose a copper wire for his torsion suspension possibly to
eliminate magnetic effects. Several posts have noted that the linear
force due to spring extension (in this case torsion) counters a
 non linear force. If the two forces are graphed in quadrants either
 side of the x axis, the controlling nature of the resultant force's
slope is made clear.

I expect Tim would find it quite challenging to select a fiber strong
enough to carry the experimental masses, and with a torsional constant
low enough to permit the unstable region to exist.
    I would enjoy seeing an estimate of the fiber's diameter.


brian whatcott <inet@intellisys.net>  Altus OK
                Eureka!