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The Attractiveness of Magnetic Fields

6 minutes

(Describer) A machine burns lines into wood, drawing rectangles that form the letters MIT. They turn into a red and grey logo. Title: Massachusetts Institute of Technology.

(Describer) Title: The Attractiveness of magnetic fields. In an animation, a stick figure wears a dress.

Hello. Today I want to introduce you to magnets and magnetic fields.

(Describer) A magnet appears.

Magnets are materials that have an invisible force that surrounds them and allows them to attract or repel other materials.

(Describer) On a translucent surface...

Here is a bunch of tiny metal filings. Let's see what happens when a magnet is introduced underneath. The small metal filings are suddenly attracted to the magnet.

(Describer) Clumps of them gather on top of it.

That invisible force drawing the filings to the magnet is called a magnetic field. We can make out the shape of the magnetic field as we move the magnet away. If magnetic fields were visible, they would look something like this.

(Describer) Arrows arch between positive and negative.

Magnets--in other words, materials that produce magnetic fields-- can be found in nature or can be constructed by people.

(Describer) Arrows also go toward the south and away from the north pole.

But what causes a material to produce magnetic fields? Well, let's take a look inside this magnet.

(Describer) Three figures orbit a ball.

Here's an atom. See those little fellows moving around? Those are electrons. Let's take a closer look at them. Electrons are subatomic particles that have a negative charge. An electron is a very small thing that has plenty of energy.

(Describer) A blue electron smiles.

They are everywhere... But wait a minute. If electrons are everywhere, why isn't everything a magnet?

(Describer) An electron sleeps.

Well, in some materials, electrons are not very active. This makes those materials seem nonmagnetic.

(Describer) One spins.

In other materials, electrons are very active and generate magnetic fields, but sometimes these electrons are positioned in opposite directions... Oh, no! Oops!

(narrator) ...causing the magnetic fields to cancel each other out.

(Describer) Two crash into each other.

However, when many electrons are aligned, a magnetic field strong enough for us to observe its effects is created.

(Describer) How to make a simple magnet.

A simple representation of what we've learned so far about electrons is turning an average screw into a magnet. We will need an iron screw, a common magnet, and paper clips for demonstration. Notice that the screw doesn't initially display any magnetic properties.

(Describer) It doesn’t attract the clips.

All we have to do is stroke the screw with the magnet in the same direction.

(Describer) The magnet’s rubbed against the screw.

What we are basically doing is causing the electrons in this screw to realign parallel to each other. Well, it's time to test the theory. If what we know about electrons is true, then this screw should be able to generate a magnetic field.

(Describer) It picks up a clip.

And there it is.

(Describer) An electron rides in a boat on water.

Another fact about electrons is that when they flow through a conductor, these electrons align in the same direction, creating a magnetic field. This is how electromagnets are created. To build an electromagnet, all you need is another screw, some copper wire, and a battery. We will be using safety gloves to protect our hands from the electric current. We will use a couple of staples for demonstration purposes. The current will run through the copper wire. In other words, this is our conductor. Wrap the wire around the screw as many times as you can, leaving a few inches of wire loose on both ends. The electrons in the current will align as they float, creating a magnetic field that will be channeled through the screw. Now take the loose ends of the wire and attach them to the ends of the battery.

(Describer) ...wearing a glove.

Remember to always handle electricity under the supervision of an adult and always wearing the appropriate protective equipment, like gloves.

(Describer) One end of the wrapped screw picks up a staple.

Success! We've created an electromagnet. Magnetic fields are important because they are everywhere. Engineers and scientists use magnetic properties to develop products and services used every day. Magnets are used in things like pickups in an electric guitar. The strip on credit cards is composed of tiny magnetized particles that allow us to store information. There are even high-speed trains that levitate above the rails using electromagnets.

(Describer) ...called MagLev.

We hope this introduction to electrons and magnetic fields has ignited your curiosity. Stay curious and have fun.

(Describer) Accessibility provided by the U.S. Department of Education.

Accessibility provided by the U.S. Department of Education.

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What causes a material to be magnetic? Learn the properties of magnets and how magnetic fields are produced.

Media Details

Runtime: 6 minutes

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