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 zero volts, the motor doesn't do anything. Now let's set the
power supply to produce 1 volt. Immediately you can see that there is 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 bigger pushing force, more
current is flowing. 2 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 communications 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 is 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 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
(light blows up) Hmm... a little too much current flowed... I guess we need to learn 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. 1 joule is enough energy to power this flashlight
for 1 second. 3 joules is enough energy to
power this flashlight for 3 seconds. And 90,000 joules is the energy required to
power this microwave for 1 minute to make a cup of tea. We'll talk more about energy and 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
x 10^18 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 x 10^18 electrons
is equal to 1 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 1 ampere is equal to 1 coulomb of charge flowing per
second. And 2 amps is 2 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
coulomb's 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 a 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 are supposed to say, is that there
is 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 is what makes
this a 9 volt battery. Over here, in casual conversation we might
say this is a 5 volt USB port. But what we really mean to say is
that there is 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,
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