It doesn't matter what you call them, the important part is that they are different. We can call them Red and Blue. Like charges repel .
Opposite charges attract .
Older audiences already know about charges. You may want to eliminate this demo for audiences that don't have kids younger than 5 th grade or so. Tell the audience we're switching gears and we're going to talk about how electricity works. Ask them for examples of things that use electricity. Ask if anyone knows what electricity is made of.