Most of us have experience playing with and using magnets. But did you know all materials are magnetic to some degree? What we actually call a magnet, however, is a material that has a strong enough magnetic force for humans to feel. But what exactly is that force? Where does it come from?
If you have studied chemistry, you know that within an atom there is a tiny particle called an electron. Those electrons have an electric charge and they create a current as they spin around the nucleus of an atom. That current gives the electrons a magnetic force. In most matter, that magnetic force is neutralized because there are equal numbers of electrons spinning in opposite directions. It’s something like adding positive and negative numbers: if you add -2 and +2 you end up with zero.
Use this activity to help children understand this concept: have them line up along a rope. Have each child grab on, then number the children 1 or 2, alternately. Have the ones pull on the rope in one direction, and have the twos pull on the rope in the opposite direction. What happens to the rope? Nothing! This is similar to the way the currents of electrons balance each other out in most matter.
In a few substances (namely iron, cobalt, nickel, and a few alloys of rare elements) the electrons are spinning in mostly the same direction, and this makes them magnetic.
Let’s investigate the magnetism of objects around us!
Testing the Magnetism of Everyday Objects
You will need:
- a bar magnet
- a variety of small magnetic and non-magnetic items, such as:
- copper wire
- paper clips
Some children might think that all metal objects are magnetic, so be sure to include some metal objects that are NOT magnetic in your assortment.
Create a chart for the children to make a guess about which objects are magnetic and which are not.
Now have the children use the bar magnet to test each object and record their results.
Discuss what happened. Which objects were magnetic? Were all the metal objects magnetic? Were you surprised by any of your results?
What did all of the magnetic objects have in common? They were all metal (or at least had metal in them – the coated paper clips are still magnetic even though you can’t see the metal). But do you remember why they are magnetic? It is because the electrons in their atoms are spinning in mostly the same direction. The magnetic metals that we see most often are iron, nickel, and cobalt. Many types of steel are also magnetic because they are made mostly from iron.
Magnetic materials can actually become magnets when their electrons get lined up so that their force becomes directional, or polarized. This can be done with an electric current or through contact with the magnetic field of another object. Let’s look at the magnetic field of a magnet, and then let’s make a magnet!
For this activity, you will need:
- iron filings
- two bar magnets
- a piece of cardstock
Place one of the bar magnets underneath the piece of cardstock. Gently sprinkle the iron filings onto the cardstock where the magnet is.
Can you see by the pattern that the iron filings make where the magnetic force is the strongest? That’s right – the magnetic force is strongest at the poles! Why would that be? Imagine the electrons inside the magnet. Their force is all going in the same direction, like this:
That is what makes the magnet a magnet! That is also why we say magnets have poles. The poles are really a description of the direction of the magnetic force.
Now take several magnets and experiment with sticking them together. What do you notice? The N poles stick to the S poles, but repel the other N poles, right? And the S poles repel each other too. Do you understand now why that happens? Let’s imagine the inside of the magnets again. When the N pole of a magnet faces the S pole of another magnet, their magnetic force lines up.
Let’s take a closer look. Place two bar magnets with an N pole close to an S pole, but not touching. Place the cardstock over them and sprinkle the iron filings over them again. What do you see?
Look at how the attractive force between the N and S poles grabbed onto all those iron filings!
When two S poles or two N poles face each other, their magnetic forces are going in opposite directions, so they repel each other.
Their forces look something like this:
Place your bar magnets near each other again, this time with two like poles facing each other, as close together as you can get them. Place the cardstock on top and sprinkle your iron filings over them.
The repulsive force between the two S poles pushed away all the iron filings! Pretty cool, huh?
Let’s make a magnet!
Now that we have learned what a magnetic force is, let’s create one!
For this activity, you will need:
- a steel nail (make sure it is NOT galvanized – galvanized nails are coated in zinc, and zinc will not become magnetized).
- a strong magnet, such as a neodymium magnet
- a few paper clips
Hold your nail and rub it in one direction with the magnet. Make sure you only rub in one direction or it will not work. You are lining up the electrons in the the nail. When you have rubbed the nail for a minute or two, try picking up the paperclips with the end of your nail. If it does’t work, rub the nail with your magnet for another minute or two, again – make sure you only rub in one direction! Keep testing your nail until you can pick up the paper clips. Congratulations! You have made a magnet!
The Earth is a Giant Magnet
What else do you know of that has a north and south pole? That’s right – the Earth! The Earth is a giant magnet! This is why you can use a compass to find a direction – the compass needle lines up with the magnetic field of the earth to point to its magnetic north pole.
Let’s make a compass!
You will need:
- a bar magnet
- a compass
First, use the compass to find north. Make sure your magnet is not near the compass when you do this, since the compass needle will be attracted to the magnet. Next, tie the string around the center of the bar magnet and tape it in place. Tape the other side of the string to the edge of a table or ledge of some kind so that the magnet is hanging freely. Check and see which direction the north pole of the magnet is pointing. It should be pointing north because it is lining up with the magnetic field of the earth. This is how a compass works!
Bonus! Looking at Magnetic Fields with Ferrofluid
Something fun to explore when studying magnetism is ferrofluid. Ferrofluid is basically tiny magnetic particles suspended in liquid. Because they are in liquid form, when they get close to a magnet, they take on the shape of the magnet’s magnetic field. It’s pretty cool to watch. Pour the ferrofluid into a petri dish, then gently place a magnet under the bottom of the petri dish. Try it with different shapes and strengths of magnets and see what happens. You can even move the magnet around the bottom of the dish and make the ferrofluid move. You can also try putting on a latex or nitrile glove and touching the ferrofluid spiky ball. But don’t touch it with your skin or clothes because it will stain!