What is an Electric Circuit? Video Lecture | Science Class 7

Have you ever wondered how a flashlight works?
Sure, it seems pretty simple...all you have
to do is move a switch or press a button,
and...ta da!
The light comes on!
But what really makes the light go on?
Right you are, Squeaks!
It’s electricity that makes the light go
on.
You probably already know something about the electricity that powers things in your house.
Well, the electricity in a flashlight comes
from the batteries that are inside.
Electricity flows from the battery to a light
bulb.
And when the electricity goes through the
bulb, the flashlight lights up!
But the electricity doesn’t just jump from
the battery right to the bulb.
In order to get from the battery to the light
bulb, the electricity has to go along a specific path.
And that path is called a circuit.
If you listen to the word "circuit", it kind
of sounds like a shape you might know.
Let's name some shapes, and see which one sounds like “circuit!”
Triangle...no...square...no...I know, circle!
And if you look at a circle, you see that
it goes around and around and doesn't have
any spaces or gaps in it.
And that’s true of a circuit, too!
There can’t be any spaces in the path that
electricity takes to get from a battery to
a light bulb.
In a circuit, if electricity doesn't have
a path to travel on, it stops.
It’s a little like a train on train tracks...when
there’s no more track, the train stops.
So let’s see how a simple circuit works.
The battery is what we call the power source
… that is, it’s where the electricity
comes from in this circuit.
Electricity flows from the power source on the path of the circuit.
And a lot of the time, that path is made by
some kind of a wire.
The circuit then leads to whatever we want to power.
In this circuit, that’s a light bulb.
As the electricity goes through the bulb,
the bulb lights up.
The electricity leaves the bulb, and flows
back through the battery.
Then it follows the circuit all over again!
As long as there are no spaces in the circuit, the bulb will stay lit.
But what if we want to turn the light on and off?
Then we have to break the circuit, which means we need to put a space in it somewhere to
stop the flow of electricity.
So...we use a switch.
A switch allows us to make a space in the
circuit if we want to.
When the switch is on, there’s no space
in the circuit, and the light bulb is lit.
But when we move the switch off, we open up a space.
The electricity can’t jump over the space,
so it can’t reach the light bulb...and the
bulb stays off!
Okay, so I’m going to try to build my own
circuit using some of the parts that I have here.
I have a power source: this battery …
… and a wire for the electricity to travel
through
...and a little light bulb.
If I arrange everything just so, it kind of
looks like a circle!
But the bulb isn’t on.
That’s because I haven’t connected all
of the pieces together.
Remember, there can’t be any spaces in the circuit.
So I’ll connect the wires to the power source...then
I’ll connect one wire to the bulb…
And when I connect the other wire to the bulb and complete the circuit...the bulb lights up!
Now, I’m going to add something else to
make it work more like our flashlight does.
I have this part that looks like a button.
And I’m going to put it right here.
And look!
The bulb is lighting up.
That means that there are no spaces in the circuit.
Okay Squeaks, I’ll press the button!
Hey, the light is on now!
That means that when I press the button, the circuit is incomplete...that means there’s
a space.
And when I let go of the button, the circuit
is complete again.
The electricity from the battery can’t cross
the space, so it can’t get to the bulb and
make it light up.
The button is a switch, just like a switch
on a flashlight!
If you look around, you’ll find that circuits
just like this are everywhere, powering all
of the things around you!
Cars, trucks, and buses all use a circuit
with a battery to get started.
And circuits run through your refrigerator,
too, and in all of the other machines in your
home that use electric power in order to work.
Inside devices like phones and computers -- which
you’re using right now -- there are very,
very small circuits that use the same basic set-up as the one I just built!
Large or small, it takes a circuit to carry
the power we need to get going!
Thanks for joining us on SciShow Kids.
And special thanks to Google Making Science
for helping us make this video!
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