||Here a student is holding a Tesla coil--what looks like a giant hypodermic needle.
The end is purposely pointed in order to concentrate electrons--the repulsion gets
them to leak out faster. On the way to the metal sphere of the electroscope,
electrons excite air molecules. Electrons from those molecules jump to higher
energy levels, and as they eventually fall back to lower levels, they emit light.
(See feint blue "lightning bolt" in picture.) The electroscope becomes negatively
charged, causing its thin leaves (gold-coloured) to repel. But the discharge of electrons is so intense that some electrons go right through the electroscope, as can be seen by another mini-lightning bolt at the bottom of the thin rod holding the gold leaves.
||Although a dry day, it's not a windy one. As the girl moves down the slide,
friction causes electrons to either come off the plastic slide or off her clothes.
In either case, each individual hair has an identical charge and the hairs try to get
as far from each other as possible. Why hasn't my son gathered static?
His hair might not be as dry, or his jeans don't gather static as easily as the fabric
of my daughter's pants.
|A balloon has been rubbed on my daughter's hair, either
causing electrons to move from her hair to the balloon or vice-versa.
Regardless of the details, the consequences will be identical. The balloon
and hair are of opposite charge and the attractive electrostatic force acts over a distance. Since the individual hairs have the same charge, they also repel each other.