What Causes Sparks Between Charged Metal Plates in a Pendulum Experiment?

[jsmith613]

I saw the following expt:

Two metal plates of zinc, one charged + the other charged - with a pendulum coated in Aluminium foil between the plates. When the plates were too close, sparks arose between the pendulum and the plates.

Is this due to the escape of charges. If not, then what are the sparks due to

 

[Matterwave]

The sparks would be the charges moving from the plates to the aluminum foil. Air is a good insulator of charges, usually charges cannot flow in air; however, if you have a high enough voltage you can produce these discharges (in essence turning the air around the moving charges into plasma, which DOES conduct electricity). This is basically lightning (in minuscule form).

 

[jsmith613]

in essence turning the air around the moving charges into plasma, which DOES conduct electricity)

are you saying that the air disperses