and so this is called coulomb's law. coulomb's named after a man about 150 years ago by the name of james j... >> law. >> law. right on. okay. and newton's law of gravity is named after a dude named... gravity. gravity. okay. we got that. we got that, okay. but we have these two things here. and all the coulomb's laws said is, "hey, the force of attraction are repel, oh, one difference, electrical forces can attract or repel." oh, so you can shield out electrical forces. gravitational forces only attract. there's no way to shield them out, but you can shield electrical forces. but it just simply says, "the amount of attraction or repulsion "depends upon how much charge you're talking about and how far away the charges." if they're very, very far away, then the force will be very, very weak. if they're close, close, close, the force will be strong. just exactly what you would expect. the same thing you'd expect with planets in the universe. planets far--very, very massive, more force of gravity, close together, more force

- coulomb. - coulomb. so one joule per one coulomb is said to be an electrical pressure of one volt. so that's what voltage is, energy per charge. we saw the dome was charged up to thousands of volts. so trisha touched that thing, thousands of volts. why wasn't trisha zapped? well, she zapped a little bit, but why is she still here today? enormous amount of energy per charge, okay? but not very many charges. if trisha went home tonight and took a bobby pin and stuck into 110 volts at home, honey, trisha wouldn't be here next time maybe, yeah, okay? she'd be hurt. you know why? that's not so much energy per charge. but how many charges are gonna flow when you stick into the power company socket, a lot or a little? it begins with a l. - a lot. - a lot. so there might be a little energy per charge, but so many that total energy going through you is very uncomfortable. but the energy that came from the van de graaff generator, a lot of energy per charge, but if not many, many charges, then not much total energ