Hi. It's Mr. Andersen and today I'm going to be talking about electricity
and electric circuits. Scientists have known about electricity for a long time. In fact
the word actually comes from the word amber. Because they realized that you could rub amber,
which is essentially dried out sap with fur and you could generate a static charge. If
you've ever gone down one of these new plastic slides, you've come out with a lot of static
electricity. And what is static electricity? Well let me show you. Here I've got a, I don't
have a balloon but I have a rubber glove. And so I've blown it up. And if I rub this
on my head over and over and over you can actually start to hear static electricity
building up. And what it's doing is it's actually pulling electrons off of my hair. And it's
putting those electrons on this balloon. What's left in my hair? Well there's less electrons.
And so my hair now has a positive charge. And this has a negative charge. But it's not
going anywhere. It's sitting there so we call that static electricity. And so the reason
that this kids hair is standing up on end is that all of these strands have positive
charges on it because they're missing their electrons. And like charges repel. So they're
all pushing on each other. And that's why they're all pulled apart. That's why you could
touch the end and get a shock. What is that? It's simply a flow of electrons. And so static
electricity is where it stays in one place. But the real revolution took place when we
could actually make circuits and we could control and use that electricity to do things.
Before that it was mostly steam power. And once we had the arrival of electricity then
we really had the next revolution or this digital revolution. You probably don't think
about it all the time but our whole society now is run by electricity. So if you search
something in Google, you don't realize this, but you're consuming energy at that point.
Because you're making a search and so Google has to go search through their database for
that quote unquote answer. And so they use a huge amount of energy. It's one of their
big costs. And so they try and make their data centers as efficient as they can. They'l
try to put them towards areas where they can get cheap and available energy. So how does
electricity work? Well this is not a great analogy but it's an analogy that works fairly
well. And I stick with it. And so if we have a battery like this. How does that store energy?
Well a way to think about it would be the same way that we store and move water around.
And so this is a giant water tower in Finland. And so if we break apart how that works, they
have underneath the ground they have a pump. And that pump pumps water all the way up into
the top. And that water is just sitting there. And so that water sitting there has a certain
amount of potential energy. And in a battery the electrons have an amount of potential
energy as well. And so we call that push or that stored energy a voltage. Okay. So let's
say I want to use some of that. Let's say I turn my faucet on here in my house or I
flush the toilet here in my house, well we've got all that energy and so it's going to flow
in this direction. And so the flow of water through this water circuit is similar to the
flow of electrons in an electric circuit. Now this diagram is not quite complete. Because
what happens after that water is done? Well we first of all have to clean it. But after
we've done that it goes right back here so that we can pump it up again. And if there's
any break in that circuit we call that an open circuit. This whole system wouldn't work.
And likewise if we ever have a break in an electric circuit, we can't move that electricity
as well. And so today I just briefly want to talk about simple electric circuits. And
show you how electric diagrams work. There are a few symbols that you should know. The
first one is the idea of a battery. On a battery there's going to be a positive side. And so
on this battery right here the positive side is going to have that little bump on it. And
then it's going to have a negative side. And so the symbol in an electric circuit for a
battery, we're going to have a top and then we're going to have a bottom like that. And
then it's going to be connected with lead or wires that go out the other side. And so
this is the symbol for a battery. And on a battery this is the positive end. So the wider
side is going to be the positive end. And then this would be the negative end. Okay.
What about a wire? Well a wire is really simple. A wire is simply going to be a line in a circuit.
Let me try to make it a little straighter than that. Sometimes lines will pass each
other. And so we want to make sure we understand if those wires are connected or not. And so
we usually put a dot here that represents that those two wires are connected. And so
this right here would be two wires connected. So electricity could flow through it. But
if you just have wires crossing each other inadvertently we don't usually don't draw
that dot to connect them. Okay. Next thing. There are things that actually slow down the
movement of electricity and we call those resistors. And here are some resistors right
here. I'll talk in a little bit more detail later. You can actually look at the color
bands on it. And you can tell how much resistance there is. But a resistor is going to be anything
that slows down the movement of those electrons. Or impedes their movement. And so the symbol
for a resistor is this. It's just up and down lines. And then we have leads on either side.
Okay. Next we have a light bulb. A light bulb is connected. So you can actually see that
electricity will flow in the bottom. So there's a little bit of metal on the bottom. And then
it's going to flow out on the side. And so it's connected all the way through the lightbulb
through a filament. And then it goes all the way down to the bottom. And so the wire goes
through it. It's high resistance wire that goes through right here. And so it gives off
a lot of heat and light. And so the way that I'll draw a light bulb to show that it's connected
all the way through is to draw a loop. And then I draw the bulb around the outside. Next
we've got a switch. A switch is simply an opening in the circuit. And so this would
be like a light switch. And so a light switch is drawn like this. We just have a switch
like that. And then if it was a closed switch, we would just have it like this. And so this
would be an opened switch. I'll try to make that a little straighter. And this would be
a closed switch right here. So electricity can flow here. But it couldn't flow through
here. And the reason it can't flow through here is that water or excuse me, electricity
is not able to move through the air. And so we almost call that an infinite amount of
resistance. And then the last thing we have is a potentiometer. So I said that wrong but
a potentiometer works like this. We've got a variable amount of resistance. And so we've
got an arrow. And then we've got a wire going out the other direction like that. And so
electrify comes through this direction. And then it goes out this direction. But we can
move this back and forth. So we can vary the amount of electricity that moves through it.
If you've ever used a dimmer switch in your house you've seens that a dimmer switch just
looks like this. So how does that work? We're turning the amount of electricity that can
move through the potentiometer and so we're letting either more electricity or current
flow or less. And so we can get more light or less. So those are the circuits. Now all
I want to do is just do a little bit of practice. And I've got some pictures here. I think I've
got just three of them. So if you want to pause and then try to sketch out what that
circuit would look like, you could do that. So here we've got a simple battery. And then
we've got a light bulb. So if I were to draw this, I tend to draw my circuits on the left
side or my batteries on the left side. So I'm going to draw my battery first. So this
right here is the positive end. And so I'm going to draw my battery like that. Now I'm
boing to draw a light bulb. And then it's going to go right back to the battery. And
then we put a bulb on it like that. And so this is what the electric circuit would look
like. It's simply has a battery here. So this would be the positive end and then this is
going to be the negative end. Electricity is going to flow through this loop and it's
going to light the bulb. And that's a closed circuit because it goes all the way in a loop.
And so it can return. Next one. If we try this. This gets a little bit more complex.
We've got a battery. And then we've got a series of lights. So let's try that. I'm going
to draw my battery here on the side. So this is my battery. And I like to kind of make
this as simple as I can. So this is a wire here. A wire here. And a wire here. And so
what we have is three loops. And so I'm going to draw one loop, so I'm going to go from
the top to the bottom. And so this would be my first loop. That's got a switch that's
actually closed. So I'm going to draw it like that. It then has a light bulb. And then it
goes back to the battery. My next loop over here. We've got the same thing. So it's got
a switch. It goes through the light bulb. And then it goes back. And then we've got
my third loop. So my third loop goes like this. It's got an open switch. It's got a
light bulb. And then it's going to go back to the battery. And so this would be a circuit
diagram for that. Electricity can go all the way around. There's actually three pathways
that it can go. You can see right here that since it's open, so since we've got an open
loop right here, electricity can't go through that. So we can't have electricity going through
here. So we call that a high amount of resistance. So where's the electricity have to go? It
has to go through the other loops. And so let's go look if that's right. Yep. You can
see that these two lights are lit because electricity is going to move through it. But
no electricity can pass through here. So there's no light on at that point. But we have a continuous
loop to this. And a continuous loop to that. Okay. Let's do the last one. Last one. This
is a picture of the Arduinos which we are actually going to use in class. This has a
processor over here on the side. It's got electricity coming out of here. This would
be the positive end. And then this is going to be the negative end. This is called a breadboard.
And so the way breadboards are connected is that there are connections horizontally. So
there's a wire that connects all of these lines. And then on the side there's going
to be a wire that connects them all vertically. And so there's a wire connecting through there.
And so that maybe helps to trace it. I'm going to start by drawing my battery again. So we've
got our battery here. I'm going to go from the negative side. So I'm going to go from
this negative side. So you can see right here it's going to connect to a light bulb. So
I'm going to do that first. So we've got a light bulb. I'll try to make that light bulb
a little bit bigger. So now we have a light bulb. You can see that that goes through the
light bulb. It goes down to the next level where we've got a resistor. So my resistor
is going to look like this. Like that. And then it's looks like the next thing we have
is a potentiometer. And so if I go like that it's going to be a variable resistor. So it's
going to be a variable resistor. And then we've got the other side with that arrow.
And then it's going to connect back to my battery. So how does this circuit work? Well
you can vary the amount of resistance here. And so I would imagine in this circuit when
you turn this dial back and forth, it's going to vary the amount of electricity. And so
this light is either going to get bright or it's going to get very dim. And this resistor
right here is probably the role of that is to decrease the amount of current so that
we don't have too much electricity going through the light bulb. And so that would be the circuit
diagram for that. So again electricity is simply the movement of electrons. And in the
next few podcasts I'm going to talk in a little bit more detail about what is voltage, what
is resistance, what is current. How do we quantify all of those things. But the first
thing you should understand is that electricity has to have a loop. It has to make it all
the way back. If it's not and it's just sitting there, it's static electricity. Like in this
balloon. Like in my hair. And like in lightning as well. So I hope that's helpful.