, skinny pipe, yeah? and how about a lamp like this? this copper right here is relatively thick. but it's very, very thin in there where the filament is. guess where most of the resistance is across these two leads. begins with fil. - filament. - filament. in that filament is most of the resistance. and guess where most of the energy is dissipated going from here to here when it touches across the battery, right in the filament. in fact, the filament reacts a little bit. it turns white hot with heat. look at that. it's glowing. and there's your lamp. isn't that nice? now you can read books and things at nighttime without having to kill whales, and just use a battery. isn't that nice, okay? a little-- you don't need a flame. just make that little piece of tungsten wire, it gets so hot, it'll glow. ain't that glowing? of course, there's your light. kinda neat, yeah? so we measure current in amperes, amps, okay? and we measure voltage in... volts. volts. and we measure resistance in... ohms. all together now