- [Instructor] You know what a magnet is,
but did you know that some magnets can be turned on and off?
One type of temporary magnet is called an electromagnet.
So what is electromagnetism?
Well, the hint is in the name itself.
Electro for electrical,
and magnet for, well, magnet.
Let's take a moment to look at the definition
of what an electromagnet is.
Electromagnets are materials that become magnets
in the presence of electricity.
But how does that even happen?
Well, it turns out
that electrically-charged particles in motion
actually have small magnetic fields around them.
So, if we run electricity through a wire,
a magnetic field will be created around the wire.
Now, we can control the strength of this magnetic field
in a couple of ways.
We can move more electric charges through the wire
at a faster rate,
and we do this by increasing the electrical current.
The second way is to increase the density
of the charged particles,
and we can do this by looping the wire into a coil.
This gives us more charged particles
with magnetic fields in a small space,
strengthening the magnetic force.
The other thing we can control with electromagnets
is the direction of the magnetic field,
and we can do this by changing the direction
of the electricity.
So if we go back to this wire example from earlier
and change the direction
of the electricity running through that wire,
well, the magnetic fields will also change direction.
This makes electromagnets quite different
from permanent magnets.
So let's take a look at that
and compare permanent magnets to electromagnets.
Electromagnets are typically made
of loops of wire and a coil.
The wire is typically made of metal like copper
and wrapped around pieces of metal
like iron, nickel, or cobalt.
This is different from a permanent magnet
because permanent magnets don't need this wire.
Permanent magnets also have fixed poles.
You can't change the north and south poles on these magnets,
but as we now know, for electromagnets,
we can change these poles by changing the direction
of the electrical current.
So, if we have an electromagnet with a north and south pole
that looks like this
and a current flowing in this direction,
well, we can change the poles
and the direction of the current.
Permanent magnets have a fixed strength,
but we just talked about
how we can change the strength of electromagnets,
so electromagnets have adjustable strength.
And finally, electromagnets need a power source
in order to generate the electricity required
to produce magnetic fields.
Permanent magnets do not need a power source,
but this means that we can also turn electromagnets
on and off,
which is pretty cool when you think about it.
On the other hand,
permanent magnets are always on.
Now, you might be thinking
if electrical charge can affect magnetism,
can magnetism affect electrical charge?
Absolutely, let's look at how we can do that.
The only way to do this is by changing the magnetic field
around the charged particles.
This can be done by moving magnets closer
or further away from the particles
or by spinning the magnets.
In fact, spinning magnets is how most of the electricity
we use in cities and homes is generated.
A turbine spins a magnet inside a coil
to produce electricity,
and since electromagnets need a power source,
this turbine is powered by wind.
So you can see why electromagnetism
is an incredibly important force,
and this isn't the only important application of it.
We use electromagnets in all sorts of other applications,
from motors to speakers and even medical scanners.