The best place to start
the theory is to start with the initial arc. The two ladder conductors
they are connected to the energized transformer a potential voltage
between them. The dielectric separating the electrodes is air. When the
is strong enough that it overcomes the dielectric strength of the
is an arc that jumps between the two electrodes. This arc ionizes the
is plasma. The plasma rises because it is air that has been superheated
warm air rises. This propagation up the
ladder conductors continues until it reaches the top and a break in the
occurs because the gap becomes large enough that the potential cannot
the dielectric strength. At this point a new arc is formed at the
the process repeats itself.
This experiment is useful in the effect that it lets a person see an arc discharging between two electrodes and gives them an idea as to how this does effect power transmission. On a transmission line this discharging of an arc is very dangerous and is meant to be avoided at all costs.