Keep anyone with a heart condition or pacemaker away from all our electricity demos. It's not dangerous, but it can be startling. Leaving your hand on the sphere in one place for a long time generates heat. When chaining people together, it can get hot pretty fast for the person holding the Plasma Ball. Like charges repel.
Opposite charges attract.
This is at the heart of all our electricity demos. See above for a good explanation. Try not to get bogged down with a story that doesn't illustrate your point simply. After talking about these things, put your hand on the Plasma Ball as an example. This and the next several points are just illustrating these same concepts in different ways.