Voltage | Introduction to electrical engineering | Electrical engineering | Khan Academy

Voltage is one of the most important quantities and ideas in electricity. In this video, we're going to develop an intuitive feeling for what voltage means. It has to do with the potential energy of electrical charges, and that's what we're going to cover here. We're not going to do a derivation, but we are going to do an intuitive description of what voltage means.

We're going to start with an analogy to gravity. Gravity and voltage are really similar ideas. I'm going to draw a mountain here. Here's some mountainside 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.

If I put it on top of the mount 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. As it does, it can do some work; it can hit some trees. Let's draw a tree, and it can run into a tree and knock that tree around. It can hit a bear; it can bounce off rocks—all kinds of things. So that's a mass rolling down a hill.

Now, if I draw this, 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 delivers electrons to the top of the hill.

So here's an electron coming out of the battery terminal, the negative battery terminal. If I release this, it is going to roll down the hill and eventually 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 can put in different circuit components, like resistors or capacitors or anything like that, and I can 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, roll down to the bottom, doing work along the way. 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!