Experiments to Try!

• What is the magnetic power of a single coil wrapped around a nail? Of 10 turns of wire? Of 100 turns? Experiment with different numbers of turns and see what happens. One way to measure and compare a magnet's "strength" is to see how many staples it can pick up.

• What difference does voltage make in the strength of an electromagnet? If you hook two batteries in series to get 3 volts, what does that do to the strength of the magnet? (Please do not try any more than 6 volts, and please do not use anything other than flashlight batteries. Please do not try house current coming from the wall in your house, as it can kill you. Please do not try a car battery, as its current can kill you as well.)

• What is the difference between an iron and an aluminum core for the magnet? For example, roll up some aluminum foil tightly and use it as the core for your magnet in place of the nail. What happens? What if you use a plastic core, like a pen?

• What about solenoids? A solenoid is another form of electromagnet. It is an electromagnetic tube generally used to move a piece of metal linearly. Find a drinking straw or an old pen (remove the ink tube). Also find a small nail (or a straightened paperclip) that will slide inside the tube easily. Wrap 100 turns of wire around the tube. Place the nail or paperclip at one end of the coil and then connect the coil to the battery. Notice how the nail moves? Solenoids are used in all sorts of places, especially locks. If your car has power locks, they may operate using a solenoid. Another common thing to do with a solenoid is to replace the nail with a thin, cylindrical permanent magnet. Then you can move the magnet in and out by changing the direction of the magnetic field in the solenoid. (Please be careful if you try placing a magnet in your solenoid, as the magnet can shoot out.)

• How do I know there's really a magnetic field? You can look at a wire's magnetic field using iron filings. Buy some iron filings, or find your own iron filings by running a magnet through playground or beach sand. Put a light dusting of filings on a sheet of paper and place the paper over a magnet. Tap the paper lightly and the filings will align with the magnetic field, letting you see its shape!

For more information on electromagnets and related topics, check out the links on the next page.