How does an Electric Motor work? (DC Motor)

How does an Electric Motor work? (DC Motor)

If you look around your house,

you will see many devices that have electric motors,

such as kids' toys, table fans,

toothbrushes, hairdryers, and this electric cutting knife.

But how does the electric motor work?

You turn it on and somehow it starts rotating.

Why is that?

we'll cover the basics of electricity

and magnets and then put it all together

to understand how the motor works.

Let's start with something called a circuit.

You have a battery, some wires

and a device that uses electricity,

such as a light bulb.

Electricity flows through the circuit.

But as soon as there is a break in the wire,

the electricity stops flowing

and the light bulb goes off.

The path must be complete for the circuit to work.

This is best down through the use of a switch.

Electricity is flowing down the wire.

This is called conventional flow.

If we take the battery out and flip it,

then the current will flow the other way.

The light bulb will still work in either case

but there are some devices

that will work differently depending

on which way the current flows.

Okay, so that's the basics of a circuit.

Now let's come over here.

This is a magnet.

It has a north pole and a south pole.

And it likes to attract other metal objects

like these paperclips.

If you bring another magnet towards it,

opposite poles attract,

and the same poles repel.

The magnets don't have to be in this shape,

for example, some magnets might be more flat, like this.

You can think of this magnet as always on,

it's always working, you can't really turn it off.

That's why it's sometimes called a permanent magnet.

It's made up of any smaller magnet domains

that are lined up in the same direction

but later, I'll show you a type of magnet

where this not always the case.

Let's take one of our permanent magnets

and drill a hole in the center

and put it on something that will allow it to spin.

Now, bring another magnet towards it.

Our spinning magnet will immediately line up

until opposite poles are right next to each other.

Now switch out the side magnet.

The same poles repel and opposite poles attract.

If we keep switching out these side magnets,

then our spinning magnet will just keep spinning.

This concept of the spinning magnet is really important.

We'll come back to it in a moment.

Here's a metal bolt which is not a magnet.

It's made up of magnetic domains

but they're pointing in random directions.

Now let's take a wire,

wrap it around several times and then create a circuit.

The current through wires forces the magnetic domains

to line up.

That means we've just made a magnet,

or more specifically, an electromagnet.

It can do the same things that a permanent magnet can.

It can pick up pieces of metal

and it has a north and a south pole,

which will attract or repel other magnets.

But the electromagnet is special

in the sense that it can be turned on or off,

just like the light bulb.

You can't do that with a permanent magnet.

Now watch what happens when we flip the battery.

The electric current was flowing this way

but now it flows the other way.

This will cause the poles on our magnet to switch places.

North will become south

and south will become north.

This is called reversing the polarity of an electromagnet.

Instead of flipping the battery,

an easier way to do this

is to just switch the wires.

You should be aware that the electromagnet

will get very hot if it's on for a while,

just a caution in case this video inspires

any science projects.

Let's come back to our spinning magnet.

This time we'll replace the spinning magnet

with our electromagnet.

As soon as we connect the wires,

the magnet turns on and it lines up

with the side magnet.

Now, in reality, connecting these wires

would prevent the bolt from spinning freely

but what's important here

is the concept of the spinning electromagnet.

Now let's switch the wires to reverse the poles

on the electromagnet.

The same poles repel and opposite poles attract.

Now, reverse the polarity again.

Same poles repel and opposite poles attract.

If we keep switching the polarity,

our electromagnet will just keep spinning.

To make this strong,

let's bring in another permanent magnet on the side.

Notice how this side has the south pole

towards the center and this side

has the north pole towards the center.

The side magnets work together

to spin the one in the middle.

This right here shows the very basics

of an electric motor

but we need to make a few improvements.

The two side magnets can be replaced

with stronger curved magnets.

And instead of a bolt with wires,

we're gonna use a metal loop.

This is called the armature.

Connect our wires and we have a circuit again.

This time, you can think of the electromagnet

as flat like this with the south pole pointing up.

Now the armature will spin

until opposite poles are lined up.

We can keep it spinning

by switching the wires just like we did before.

But this is a lot of work to sit here

and manually