Types of Magnets. force: a push or a pull

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1 Imagine that you have a superpower. Your power allows you to move things without touching them. You can even move things located on the other side of a wall! Your power to move things without touching them is a force. This force allows you to pull and push objects; however, this force acts only on things made of certain materials, like iron. Does your power seem familiar? If so, it s because you have seen it in action many times! Do you know what the force is that can move objects made of iron? What is magnetism? Magnetism is a force between certain kinds of objects. This force can be either pushing or pulling. The force can act between two magnets or between a magnet and something made of iron. Magnets are also made of iron. force: a push or a pull The two ends of a magnet are different. One end is called the north pole. The other end is called the south pole. Any part of a magnet pulls on things made of iron and a few other metals. However, the north pole of one magnet pulls only at the south pole of another magnet. Two north poles push each other away. Two south poles also push each other away. Magnetic force is caused by certain particles that make up an object. When these particles are all arranged in the same way, the object becomes a magnet. The magnetic force of a magnet forms a pattern called a magnetic field. A magnetic field is made up of magnetic lines of force. The lines of force are invisible, but there is a way to see their shape. Put a magnet under a piece of paper and sprinkle small bits of iron on the paper. The iron bits will line up with the lines of force. You can see this in the picture on the right. Magnets come in many shapes and sizes. Iron filings arrange themselves along magnetic lines of force. 1

2 Earth itself is magnetic! You should know that Earth has a North Pole and a South Pole. If you can imagine a magnet running from the North Pole to the South Pole, then you are picturing Earth s magnet. The core of Earth is made of molten iron, and scientists believe because there is so much pressure in the center of the Earth that some of that molten iron turns into a solid. The liquid iron, along with this solid form and the rotation of the Earth, create a magnetic force. This force isn t very strong, but it is strong enough to cause compasses to always point north. The core, or center of Earth, is made of heated liquid iron ore. Magnets can be very powerful. You may have struggled to pull apart two large magnets. Magnets can even attract through non-magnetic materials. Magnetic name tags can work through several layers of fabric. Investigate the strength of a magnet s force and what materials will block the force of magnets. Gather a stack of construction paper, a paper clip, and an assortment of magnets. Does a magnet attract the paper clip through one sheet of paper? How about five sheets? How many sheets of paper does it take to block the force of the magnet? Gather some objects like paper clips and iron nails. Place an iron object on top of a desk or table. Hold a magnet below the surface and try to move the iron object through the surface material. Repeat with each magnet. Are some magnets blocked by the surface material and others are not? How does the size or shape of the magnet affect its force? Try other materials like plastic, glass, rock, and metal. Through how many layers is the force of the magnet able to attract? What materials block the force of the magnet? What materials allow the force to flow? You know that magnets can attract without actually touching an object. You can slowly push a magnet toward a paper clip and see the paper clip jump to the magnet once it is within the magnetic force field. How far will the force attract? Place one paper clip on a magnet. Attract another paper clip to the first, and another the the second. How many paper clips can you attract? 2

3 Earth is a large magnet with a magnetic field. A compass has a needle that is a small magnet. The needle always points toward Earth s magnetic North Pole. You can use Earth s magnetic field to make a magnet. You will need a compass, a hammer, and an iron rod. The iron rod should be about a foot long. (The vertical rod in a ring stand works well.) With an adult s help, use the compass to find the direction north. Point one end of the rod toward north. Hit one end of the rod with the hammer several times. This will help rearrange the iron atoms to create a magnetic field. Now you can see if you made the rod into a magnet. With an adult s help, tie a string to the middle of the rod. The rod should spin freely while hanging from the string in a level position. Tie the string to something overhead. Give the rod a gentle spin. If one end is pointing north when it stops spinning, the rod has become a magnet. Permanent and Temporary Magnets Earth s magnet is a permanent magnet, meaning it is always there. A permanent magnet is one that retains its magnetic properties for a long time. They are made of materials that are naturally magnetic, or attracted to iron. Most permanent magnets are U-shaped; these are called horseshoe magnets. Rectangular magnets are called bar magnets. The poles of a bar magnet are on opposite ends. If you have two bar magnets and try to touch both north poles together, the magnets will repel, or push away from each other. However, if you put one north pole and one south pole together, they will attract. A magnet on the front of your refrigerator is an example of a permanent magnet. An electromagnet is an example of a temporary magnet. A compass needle always points north. Horseshoe magnets contain a north and south pole, even though the poles are shaped differently than what you might think. Temporary magnets are magnets made from items that might not normally have magnetic properties. These are called electromagnets. The magnetic force of an electromagnet can be turned on or off using electricity. A wire coiled around a cylindrical object and powered by electricity creates a magnetic field. Many things we use every day, including doorbells and music speakers, use electromagnets. 3

4 What do you know? Imagine dropping three magnets into a glass tube. The picture below shows how the magnets line up in the tube. The north pole of the bottom magnet is marked with an N. Mark the remaining poles of all three magnets. Write the letter N on each north pole. Write the letter S on each south pole. Remember, if poles are the same, they push away from each other. 4

5 Exploring with Magnets Try this simple experiment with your child to see if a magnet can pull through different materials. Materials: A magnet A paper clip A cotton ball A book A plastic cup Procedure: 1. Hold the magnet close to the paper clip and observe what happens. 2. Hold the cotton ball in front of the magnet and test to see if the paper clip is still attracted through the cotton ball. 3. Repeat this process using the book and the plastic cup. Do materials block a magnet s pull on the paper clip? 4. Design a track on a piece of cardboard. Use the magnet to guide the paper clip through the track without touching the paper clip. 5