In my first video about basic electricity, you learned that current is basically the flow of electrons in a wire. And the term amps or amperes refers to how many electrons are flowing past a certain point per second. In this video, I'm going to first tell you what voltage does, then I'm going to explain what voltage is.
There's an important difference. Okay, the super simplified explanation of voltage is that volts push current around an electric circuit. Voltage behaves like a pushing force.
forcing electrons to start moving around which creates an electric current. Ok, I want to show you an example. Over here I have an electric motor with some wires connected to it.
This fancy thing is an adjustable power supply. It allows me to create nearly any voltage I want which is useful for designing circuits, but you don't need one of these to start learning about electricity. You can just use batteries.
The voltage I'm generating will be shown here. And the fun thing about this power supply is it can automatically measure how much current is flowing, and that's going to be shown here. I want you to see how when you increase the voltage going to the motor, more current flows. If we start out with the power supply set to 0 volts, the motor doesn't do anything.
Now let's set the power supply to produce 1 volt. Immediately you can see that there's current flowing, roughly 1.8 amps. And when there's current flowing, energy can flow from the power supply to the motor.
Now, let's increase the voltage to 2 volts. Now that we have a bigger pushing force, more current is flowing. Two amps.
So more energy is flowing through the motor, so obviously it's going to turn faster. And the more I crank up the voltage, we get even more current, and the motor speeds up. Okay, that's just one example of what voltage does. You can use a voltage source to power motors, light bulbs, electronics, and other things. Another important example of what voltage can do is carry useful information.
You can use different voltages as electrical signals that represent data. In this example, 0 volts or 5 volts represents binary 0s and 1s in a communication system. Now, this is way more advanced than what I want to talk about in this video.
I just want you to understand that sometimes voltage is used to power things that draw high amounts of current, but you can also use voltage as a signal. And almost no current flows at all. You just create the changing voltages with a transmitter, and detect the changing voltages with a suitable receiver.
Now remember, the whole volts push amps thing is just a helpful simplification. What's really going on here is that there's a chemical reaction inside this battery that's creating a voltage. This side of the battery is more negatively charged than the top of the battery.
Negative charges repel negative charges, so this side of the battery will push electrons away from it. Electrons push other electrons, current flows, and the electrons on the top side get attracted to the positive side of the battery, and everything flows in a complete circuit. Okay, I've been talking about what voltage does and how you can use it. Now let's talk about what voltage actually is. Voltage is a difference in electrical potential energy per unit of charge between two points.
Okay, there's a lot to cover here, so let's break all these words down into their basic definitions. Let's start out with the words potential energy. Forget about hippies and feelings for a second. The actual scientific definition of energy is the ability...
to do work. The work could be moving something, heating something, things like that. We say something has potential energy if it has the potential to do work. For example, this stretched elastic band has elastic potential energy. It's not doing anything right now, but it has the potential to do work.
If I released it, the elastic potential energy would be converted into movement, which will propel the piece of paper into my target. This battery has electrical potential energy. It's not doing anything right now, but it does have the potential to do work.
There's a chemical reaction inside it that creates electrical potential energy. And if I connect this light to this battery, we form a complete electrical circuit. Current will flow, and... Hmm, a little too much current flowed.
I guess we need to learn a little more about electricity before we try that again. Anyway, those are some examples of potential energy, and it's important to know that we measure energy with units called joules. Joules can be used to describe the amount of energy it takes to do a lot of different things. One joule is enough energy to power this flashlight for one second.
Three joules is enough energy to power this flashlight for three seconds. And 90,000 joules is the energy required to power this microwave for one minute to make a cup of tea. We'll talk more about energy in joules later in the video. Ok, so now you have an idea of what electrical potential energy means, what does this unit of charge mean?
Well, do you remember how I was saying that electrons are negatively charged particles, and 1 amp is 6.24 times 10 to the power of 18 electrons flowing per second? That's a really awkward number. And engineers hate using it.
Instead we use a standard unit of charge called the coulomb. The total charge on 6.24 times 10 to the power of 18 electrons is equal to one coulomb of charge. And since electrons have a negative charge, this charge would be negative.
You can see now that it's much easier to just say one ampere is equal to one coulomb of charge flowing per second, and two amps is two coulombs flowing per second. Now let's tie these two concepts together. When we talk about electrical potential energy per unit of charge, we mean that a certain number of joules of energy are being transferred for every unit of charge that flows.
For example, let's say this is a 1.5 volt battery. That means that for every coulomb of charge that flows from the battery, 1.5 joules of energy are being transferred. 1.5 joules of chemical energy are being converted into electrical potential energy.
Then, this electrical potential energy, or voltage, pushes electrons around the circuit, and for every coulombs worth of electrons that flow, 1.5 joules of energy are getting delivered to the light bulb and converted into light and heat. Now let's go back to my example with the motor. With the power supply set to zero volts, no current can flow. But with the flick of a switch, Now the power supply delivers 1 volt, or 1 joule per coulomb, and over here, the power supply is measuring the amount of current flowing through the motor. It's roughly 1.8 amps.
1.8 amps means that 1.8 coulombs are flowing from the power supply every second, and for every coulomb, 1 joule of energy gets transferred. So 1 volt times 1.8 amps means that 1.8 joules of energy are flowing through this motor every second. If we increase the power supply's voltage to 2 volts, the higher voltage pushes more current, and now we have 2 coulombs per second flowing.
2 volts multiplied by 2 amps means that 4 joules of energy are flowing through this motor every second. And of course with more energy flowing through the motor every second, obviously the motor is going to do more work and spin faster. Ok, now that you understand energy per coulomb, let's go back to our definition of voltage and talk about this part. Voltage is the difference in electrical potential energy between two points.
In other words, voltage is always relative. We all say this is a 9 volt battery, but that's not 100% correct. What we're supposed to say is that there's an electrical potential difference of 9 volts between this negative terminal and this positive terminal. There's a difference of 9 joules for every coulomb that flows out of the battery, and that's what makes this a 9 volt battery.
Over here, in casual conversation we might say that this is a 5 volt USB port, but what we really mean to say is that there's 5 volts between this positive power pin and this negative power pin. These two pins are used for sending digital messages, and there's a rapidly changing 3.3 volts between them which carries the information. So voltage is always measured between two points, and this is why voltage is also sometimes called potential difference. That's right, voltage can sometimes be called potential difference, tension, and a lot of other names. No wonder people get confused.
Ok, that was voltage, my next video will be linked over here. In the meantime, subscribe, thumbs up, twitter, facebook, website, yada yada yada, you know what to do.