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Transcript
Making an Electromagnet Recall that a piece of iron in a strong magnetic field becomes a magnet itself. An electromagnet is a magnet made by placing a piece of iron or steel inside a coil of wire. As long as the coil carries a current, the metal acts as a magnet and iron coil increases the magnetic field of core the coil. But when the current is turned off, the magnetic domains in the metal become S N random again and the magnetic field disappears. By increasing the number of loops in the coil, you can increase the strength of the electromagnet. Electromagnets exert a much more powerful magnetic field than a coil of wire without a metal core. They can also be much stronger than the strongest permanent magnets made of metal alone. You can increase the field strength of an electromagnet by adding more coils or a stronger current. Some of the most powerful magnets in the world are huge electromagnets that are used in scientific instruments. check your reading How can you increase the strength of an electromagnet? Electromagnets How can you make an electromagnet? SKILL FOCUS Observing PROCEDURE 1 Starting about 25 cm from one end of the wire, wrap the wire in tight coils around the nail. The coils should cover the nail from the head almost to the point. 2 Tape the two batteries together as shown. Tape one end of the wire to a free battery terminal. 3 Touch the point of the nail to a paper clip and record your observations. 4 Connect the other end of the wire to the other battery terminal. Again touch the point of the nail to a paper clip. Disconnect the wire from the battery. Record your observations. WHAT DO YOU THINK? • What did you observe? • Did you make an electromagnet? How do you know? CHALLENGE Do you think the result would be different if you used an aluminum nail instead of an iron nail? Why? 538 Unit 4: Electricity and Magnetism MATERIALS • • • • • insulated wire large iron nail 2 D cells electrical tape paper clip TIME 20 minutes