Magnets and Charge

Abstract

Objective

In this science fair project, you will investigate the effect of charge on the strength of homemade magnets.

Credits

Sara Agee, PhD, Science Buddies

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Introduction

Magnets are fun to play with on the refrigerator, because their magnetic properties make them stick to certain metallic surfaces without falling off. Magnets are polar, which means they have two ends that are different. All magnets have two poles, called north and south. Two ends of a magnet that are the same will repel, or push each other apart. Two ends of a magnet that are different will attract, or pull each other together.

Electricity and magnetism are all around us. Earth is a giant magnet, and we can sense Earth's magnetism when we use a compass. The needle of the compass points toward the north pole. Why is Earth magnetic? The magnetism is caused by motion of molten nickel and iron in the center of Earth, both of which are magnetic metals.

Electric current has a magnetic field around it. This is used to create electromagnets and electromagnetic motors. Many appliances that use electricity have electromagnetic motors in them. Electromagnets are magnets that can be switched on and off by turning the current on and off. An example is the junkyard cranes that use electromagnets to lift a car and then turn the magnet off to drop the car.

Electromagnets are only magnetic when an electric current is running through them. The strength of the magnet depends upon the strength of the current. There are many ways to change the strength of the current. You can change the strength of the source of electricity, the connection between the source of electricity and the magnet, or the direction of the current through the magnet.

In this science fair project, you will try to change the strength of a magnet by changing the number of turns of copper wire wrapped around the electromagnet.

Terms and Concepts

To do this science fair project, you should know what the following terms mean. Have an adult help you search the Internet, or take you to your local library to find out more!

• Magnet
• Metal
• Pole
• Repulsion
• Attract
• Control
• Electromagnet
• Charge

Bibliography

• Gagnon, S. (2005). How do I make an electromagnet? Thomas Jefferson National Accelerator Facility, Office of Science Education. Retrieved December 23, 2005, from
  http://education.jlab.org/qa/electromagnet.html
• KidsCanMakeIt.com (2001). Kids Can Make It: Electromagnet Activity. Retrieved December 23, 2005, from
  http://www.kidscanmakeit.com/SN0002.htm

Materials and Equipment

• Large iron nails (5)
• Insulated copper wire
• Wire cutters
• Wire strippers
• 9-V battery
• Iron filings (like the 12-oz shaker jar from Dowling Magnets: http://www.dowlingmagnets.com/)
• Paper cups (several)
• Permanent marker
• Kitchen scale, such as the Fast Weigh MS-500-BLK Digital Pocket Scale, 500 by 0.1 G, available from Amazon.com
• Lab notebook
• Graph paper

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Experimental Procedure

1. You will use four of the nails to make magnets, and save one nail as a negative control. That means that you will not charge the control magnet, and will see if it has any magnetic properties on its own.
2. To make the four magnets, wrap insulated copper wire clockwise around each nail, tightly, with different numbers of wraps: 5, 10, 15, and 20.
3. Leave about 3 inches of loose wire at each end of the nail. Cut the wire with wire cutters after you've wrapped each nail. You now have four electromagnets.
4. Strip the last 1/2 inch of wire at each end with the wire strippers.
5. Next, attach each electromagnet to the 9-V battery, one at a time, to test the strength of each magnet. Record the observations in your lab notebook.
6. You will want to connect each electromagnet to the battery in the same way. Wrap the pointy end of the nail wire to the positive battery terminal, and the flat end of the nail wire to the negative battery terminal.
7. To measure the strength of each magnet, use iron shavings. Pour your iron filings into one of the paper cups. Dip the tip of one electromagnetic nail into a cup of iron shavings and remove. What do you see? Record all observations in your lab notebook.
8. If there are any iron shavings stuck to the nail, move the nail over a clean cup to remove them. While holding the nail and iron shavings over the cup, disconnect one of the ends of wire from the battery terminal. What happens?
9. If there are any pieces of iron shavings still stuck on the magnet, brush them off into the cup.
10. Label the cup with the type of electromagnet used (5, 10, 15, or 20 wraps) or with "control," and set the cup aside.
11. Repeat steps 6–10 with the other magnets, and steps 7–10 with your un-magnetized control nail.
12. Now you need to weigh each of your cups on the kitchen digital scale and write your data in a data table, like the one shown below, in your lab notebook:

    Number of Wraps	Length	Magnetic? (Y/N)	Weight of Shavings (grams [g])
    5	1/4
    10	1/2
    15	3/4
    20	full
    none	none

13. Make a bar graph of your data. You can use graph paper or a website like Create a Graph. Do you notice any trends or patterns? How do you think the wrapping of the wire affected the strength of the magnet?

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Variations

• Magnets can have different patterns of magnetic fields, depending upon their shape. You can see the shape of the magnetic field by placing a magnet on a piece of paper and dusting fine iron shavings around the paper. Try this with magnets of different shapes and sizes. Try taking some pictures of each different pattern.
• Because magnets are polar, you can arrange a series of magnets to make a magnetic cushion. Arrange a stack of circular magnets with similar poles facing each other, alternating each time. What happens? Can you think of a practical way to put this type of magnetic cushion to use?
• Do you have an old computer monitor at home? If you get you parents' permission first, try placing a magnet up against the monitor. What happens to the image? It is very important to try this science fair project variation only with your parents' permission and guidance!

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Related Links

• Science Fair Project Guide
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• Physics Project Ideas
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