Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
Hi Jim,
The movie, I believe, is very revealing. Because of the slow ramp
up in voltage before an arc is struck, one can see the affects of
the electrostatic attraction before there is any current. As the
voltage gets larger, the rods progressively get closer. The scale
at the top of the ladder is a great visual aid. There seems to
still be a little natural response because the voltage is still
changing but is much less in amplitude than when the voltage is
applied all at once.
Once the arc occurs, the electrostatic attraction disappears for the
most part and current starts to flow. However, when the arc is at
the bottom of the ladder, the current length is very small and the
corresponding force should also be small. Notice when the
electrostatic attraction disappears. The affect is like a negative
unit step frunction and the natural response is excited at its full
amplitude. As the arc climbs, the affect of the current becomes
greater. I haven't figured out the sign of the magnetic force, but
do believe opposite currents will attrract.