Video transcript - [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. The other half of this calculation is the current. You need a larger wire to move more current. If you have a choice the higher voltage is best. These formulas are also useful in calculating AC alternating current wattage to determine the size of an inverter, which converts the DC electricity from a solar array to AC that can then be used to power lights and appliances in homes and businesses.
Appliances include a face plate which contains all of its electrical data. Lets suppose you have a microwave oven. The manufacturer will list an amp requirement on the electrical data of the face plate, which is usually attached to the back of the oven. Let's say that the rating on the face plate is 8. To calculate the watts, multiply 8. This equals watts. Now, lets calculate how much power the microwave will use in one day. If you use the microwave for 2 hours a day, then multiply the hours per day by the watts to get watt-hours per day.
So, you have watts multiplied by 2 hours, which equals watt-hours per day. When sizing a solar power system, this formula is necessary in determining the total power you use per day.
The voltage is equivalent to the water pressure, the current is equivalent to the flow rate, and the resistance is like the pipe size. There is a basic equation in electrical engineering that states how the three terms relate. This is known as Ohm's law. Let's see how this relation applies to the plumbing system.
Let's say you have a tank of pressurized water connected to a hose that you are using to water the garden. What happens if you increase the pressure in the tank? You probably can guess that this makes more water come out of the hose. The same is true of an electrical system: Increasing the voltage will make more current flow. Let's say you increase the diameter of the hose and all of the fittings to the tank. You probably guessed that this also makes more water come out of the hose.
This is like decreasing the resistance in an electrical system, which increases the current flow. Electrical power is measured in watts. In an electrical system power P is equal to the voltage multiplied by the current. The water analogy still applies. Take a hose and point it at a waterwheel like the ones that were used to turn grinding stones in watermills. You can increase the power generated by the waterwheel in two ways.
If you increase the pressure of the water coming out of the hose, it hits the waterwheel with a lot more force and the wheel turns faster, generating more power. If you increase the flow rate, the waterwheel turns faster because of the weight of the extra water hitting it.
In an electrical system, increasing either the current or the voltage will result in higher power.
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