[laughs] Oh, hello fellow scientists! Welcome back.
What? What do you mean, "What am I doing?" I am clearly conducting important scientific
research here. I am investigating how electrical currents created by moving electrons cause an
attractive force between certain materials and obviously true statements about yours truly.
By the end of today's lesson, you will be able to describe the force of magnetism,
explain what causes it, and identify magnetic materials and uses for magnets. Let's get into it.
Magnets are everywhere! They're in our toys, our electronics, our jewelry, and,
if you're anything like me, they are all over your refrigerator. But what is magnetism exactly?
Magnetism is a force exerted by magnets when they attract or repel certain materials.
Have you ever tried using a magnet to hang up a picture on your refrigerator door? You might have
noticed that the magnet and the refrigerator door seemed to stick together. Well, that's actually
the force of magnetism pulling them together. That pulling force is called "attraction."
It's not just other magnets that experience this attractive force of magnetism, though.
Other materials will stick to magnets too. If a material is attracted by a magnet,
then the material is called "magnetic." If you have a magnet lying around your house right now,
pause the video here to investigate what types of materials are magnetic. If you don't have a
magnet lying around, that's totally fine too. Just think about any past experiences and
observations you might have. Either way, jot down your thoughts in your guided notes now.
You probably noticed that most of the things that stick to magnets are metal. As a matter of fact,
the most magnetic materials out there are the metals iron, nickel, and cobalt.
However, just because something is a metal, it doesn't mean it's magnetic. If you try to move
a magnet over some silver, gold, or aluminum, then you might as well be holding a rubber chicken for
all you're going to attract. [squawk] You might have also noticed that magnets don't always
attract things. Sometimes, when you take two different magnets and try to push them together,
they just won't go. It feels like there's an invisible force field between them. Well,
here the force of magnetism is actually pushing these magnets apart, or repelling them.
So, how does any of this actually work? How can there be a force that we can't see that can act
on objects without even touching them and can both push and pull? To understand magnetism,
we have to look all the way down at the atomic level. As we know, all matter is made of atoms,
those tiny particles that are the building blocks of everything in our universe. Atoms themselves
are made up of even smaller particles, like electrons, which carry an electric charge.
In most materials, these electrons are spinning around the outside of the atom in
all different directions. However, in magnets, the electrons are all spinning in the same direction.
This aligned spinning of the electrons creates an electric current, and that's what causes the force
of magnetism. This aligned electron spinning also creates a magnetic field. That's the area
around the magnet where the magnet's force can act on. That's how magnets can attract and repel
things without even having to touch them. You can actually visualize a magnetic field by placing
lots of little bits of iron filings on a surface around a magnet. The iron filings are magnetic,
so they'll align to the magnetic field, making it visible. It's pretty cool, right?
So, since all these electrons are facing the same direction, there is a pretty clear front
end and back end to a magnet. We call these ends the north pole and the south pole, respectively.
When it comes to magnets, opposites attract. So, if you try to match a north pole to a south
pole of another magnet, then they will attract. However, if you try to put together two north
poles or two south poles, then the magnets will repel. Once we understand how magnets work, we can
use them for all sorts of useful things, besides just displaying your hard work on the fridge.
For example, magnets are used in MRI scanners to create an image of the inside of a person's body,
which doctors can use to help people when they're sick. Electromagnets, which are super strong
because an extra electrical charge is run through them, are used for big jobs like construction.
One of the newest ways to use magnets is with maglev trains, which use the attractive and
repulsive forces of magnets to hover a train above the track, eliminating the
force of friction that's normally on train wheels. Using only the force of magnetism,
maglev trains can move much faster than a normal train, up to 375 miles per hour.
Can you think of some other places where we use
magnets? Pause the video here and write down your ideas in your guided notes.
Now, most of the magnets that we use in our day-to-day lives are man-made, but there are
magnets in nature too. Take lodestones, for instance. These are magnetized pieces of the
mineral magnetite. It's believed that they get magnetized by the electric current from lightning
strikes. People used lodestones in ancient times as the first compasses. One of the biggest natural
magnets out there is actually the Earth itself. The core of the Earth is made up of molten iron
and nickel, so the movement of those liquid metals creates a magnetic field over the entire planet,
complete with its own north and south pole, just like any other magnet. Now, Earth's magnetic north
and south pole aren't exactly where its geographic north and south pole are, but they're actually
pretty close. Earth's magnetic north pole is about 500 miles away from the North Pole. The Earth's
magnetic field is the reason why compasses are so useful for navigation. They point travelers north
because the magnets in a compass are pulled to Earth's magnetic north pole. Pretty cool!
Let's review everything we've learned today about magnets. Magnetism is the force exerted by magnets
when they attract (pull) or repel (push) certain materials. Iron, cobalt, and nickel are the most
magnetic materials. Magnetism is caused by the flow of aligned electrons. Opposite poles of a
magnet attract, and like poles repel. Magnets are extremely useful in technology and innovation.
To learn more about magnets and magnetism,
be sure to check out the activities and practice questions for this lesson.
Now, if you'll excuse me, with all the magnets in the world, I gotta start spreading my message. So
until next time, remember: science is all around us. See you next time – Wha? Woah!