You’ve probably measured, or seen someone measure voltage in a circuit
using a meter like this. But what is voltage?
Is it energy, or power, or something else? I’ll answer that in this video.
Let’s start with the electrons. Electrons are moving through the wires
and the various parts of this circuit. But what’s making those electrons move?
The chemical processes going on inside these batteries are making them move.
Or, it could be a generator instead, like the one in my gravity light,
in which case it’d be moving magnetic fields that make the electrons move.
Or it could be solar cells, in which case the sun’s energy
would be interacting with the atoms in the cells to get the process going.
Or any number of other things could be supplying the energy.
Before we can say what voltage is, we need to know a little more.
Each electron has a negative charge. What is charge?
Charge is a property of fundamental particles, including electrons.
That property involves certain behaviours, but for this video
what’s important is that the charge can be quantified,
it can be counted. Charge is measured in units called coulombs.
To get just one coulomb of charge it takes 6.241×10^18 electrons.
That’s 6241 followed by 15 zeroes number of electrons.
That’s a heck of a lot electrons for one coulomb of charge.
So I’ll just draw 1 coulomb of charge as the amount of charge in this clump of electrons,
even though in reality the electrons are spread out.
Let’s look at where the meter is connected. Notice that one meter probe is connected to
one side of this LED and the other meter probe is connected to
the other side. Again, we have electrons going through this
diode. A lessor amount also goes through the meter
so that we can make our measurement. It doesn’t matter which path we pay attention
to, but we’ll pay attention just to the ones going
through the diode. Finally we can say what voltage is.
Voltage is the amount of energy that’s used to move each unit of charge,
each coulomb, from here to here. That’s why we put the meter probes on either
side of the diode, or whatever we’re checking the voltage of.
Voltage is the amount of energy used to move each coulomb of charge
from one side of the diode to the other side. While charge is in units of coulombs,
energy is in a unit called the joule. 1 unit of energy is 1 joule.
So voltage is in units of joules per coulomb. You’ve probably heard of a different unit
for voltage called the volt. Saying 1 volt is the same as saying 1 joule
per coulomb, except that the word volt is just taken from
a famous scientist’s name, whereas joules per coulomb tells you
that we’re dealing with energy per charge; it’s much more descriptive.
So voltage is an amount of energy. But the important thing is that its the amount
of energy per unit of charge.
That’s a very important point so let me illustrate it.
Let’s say this is what’s going through the LED.
And let’s say that the voltage is 3 joules per coulomb, or 3 volts.
If the voltage is 3 joules per coulomb, that means there are 3 joules of energy moving
this coulomb of charge, 3 joules of energy moving this coulomb,
and 3 joules moving this coulomb. That’s a total of 9 joules of energy,
but the voltage is only 3 joules per coulomb, 3 volts.
Now let’s increase the amount of charge moving from here to here.
But the voltage is still just 3 joules per coulomb.
3 for this coulomb, 3 for this one,
and so on. There’s a lot more total energy this time,
but the voltage is no higher. It’s still just 3 joules per coulomb, 3 volts.
And that’s what voltage is when talking about charge moving
through a circuit like this. Well, thanks for watching!
See my youtube channel, rimstarorg for more interesting videos like this.
That includes one explaining what electric current and amps are.
One about my gravity light version 2, the machine with the generator that I showed.
And for variety, one on how a rocket works to get from Earth to orbit
using SpaceX’s Falcon 9 as an example. And don’t forget to subscribe if you like
these videos, or give a thumbs up, or leave a question or
comment below. See you soon!