- [Voiceover] Voltage is one of the most important quantities and ideas in electricity, and in this video we're gonna develop an intuitive feeling for what voltage means. But it has to do with potential energy of electrical charges and that's what we're going to cover here, we're not gonna do a derivation, but we are going to do an intuitive description of what voltage means. We're gonna start with an analogy to gravity. Gravity and voltage are really similar ideas. I'm going to draw a mountain here. Here's some mountain-side with snow on it. And I'm going to put a mass here, here's a mass of some mass M. And it was lifted up to the top of the hill somehow, by a ski lift, by a mountain climber, something like that. And if I put it on top of the mountain and I let it go, the potential energy that it has is going to be dissipated as kinetic energy and that mass is going to roll down the hill to here. And as it does, it could do some work. It could hit some trees, let's draw a tree. And it could run into a tree and knock that tree around. It could hit a bear, it could bounce off rocks, all kinds of things, so that's a mass rolling down a hill. Now if I draw, this is a way to think about voltage, think about voltage as being another mountaintop, and this time we'll put a battery in here. This is our battery, this is what a battery does for us, it actually builds our mountain. The battery actually delivers electrons to the top of the hill, so here's an electron coming out of the battery terminal, the negative battery terminal. And if I release this, it is going to roll down the hill. And eventually it's going to return to the bottom side of the battery. But the same thing, this is the image you have in your head when we hook up a circuit. Along the way I could put in different circuit components like resistors or capacitors or anything like that, and I could make this electron do work and bump into things as it goes down. So, the amount of voltage here is proportional to the height of this mountain. A high voltage is a high mountain and a low voltage is a low mountain. The electrons are pushed out the top by the battery and roll down to the bottom doing work along the way, and this is where we do our circuit design. That's what we're doing over here, we buy batteries and we do our circuit design and study over here. So this is a pretty good analogy for thinking about voltage as you begin to build your circuits. See you next time.