Do it Yourself Electromagnet

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Engineering, Physics: Electromagnetism, Circuit Building
Grade Range: Middle School, High School
Format: Hands-on

Electromagnetism is a complicated topic that can be presented simply. This demonstration will help students see what physical factors affect the ability and effectiveness of their own electromagnets. This can be a classroom competition for students, to see which team can make the strongest magnet!

Contents

Materials

  • Electrical Tape
  • Non-Insulated Wire
  • 9V Batteries (one per group)
  • 6" Nails (one per group)
  • Paper Clips
  • Oven Mitts (one per group)

Safety Precautions

Please read the General Safety section of the Demonstration Safety page before performing this demonstration.


Demonstration

  1. Provide each student group with:
    • 4 feet of wire
    • 3 feet of electrical tape
    • A 9V battery
    • A nail
    • an oven mitt
  2. Let the groups know that they will have 30 minutes to create their own electromagnet, using the supplies given, and to test the strength of it. Explain that the oven mitt is because the battery will get hot when they are trying their electromagnets, so they will want to wear it while holding the battery.
  3. When each group finishes preparing their magnet, they are to bring it over to your table/desk. On one side of your desk there will be a pile of paper clips, and they must try to move as many of them across the desk using only the electromagnet they made. The magnet has to lift the clips off the table/desk and keep them suspended the whole journey to the other side. If any fall off during the journey, then they do not count towards their final score. Each group can try a maximum of three times, and the try with the highest number of clips is their score.
  4. After all groups get their attempts in, show who won 1st, 2nd and 3rd. Ask the three groups to show what they did to make their magnets, and compare the methods to show what made these magnets the strongest.


Why This Works

Electromagnetism is when you create a magnetic field by using a flow of electricity. In physics, this topic is often discussed when looking at moving charges, and studying how a moving charge creates a magnetic field around it. Electromagnetism also talks about how something that has a magnetic field can induce, or generate, a charge in a surface as it moves by. This experiment we see this effect happen when trying to make an electromagnet. Iron is magnetic, but outside of a magnetic field it doesn't usually stay magnetic. When we wind the copper wire around it and connect it to a battery, we then have a moving charge through the wire. This generates a magnetic field, which then causes the nail to become magnetic!

In engineering, we can look at how to manipulate these electromagnetic properties by adjust the physical properties of a material. The top three groups all had tightly wound their wires around the nail. This tight coil is called a Solenoid, and solenoids are great for increasing the amount of charge that we induce in another surface, in this case the nail. Some of the groups also insulated their wire using the electrical tape. If they insulated the entire solenoid after winding, then it helps prevent any energy loss to the air, which increases the strength of the magnet. If they insulated the wire before making the solenoid, then it will be the strongest, since the wires can no longer conduct sideways through each other, and the charge has to travel farther. This will make their magnet extra strong!


Additional Information

  • Expect to see all kinds of techniques to create the best magnets. Be prepared to see some very unique or surprising ones as well!
  • The electromagnets will heat up due to the Joule-Lenz Law. An explanation for this can be found with the Homopolar Motor demonstration, which pairs well with this one.
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