Chapter 8: Electromagnets

Unit: Energy and Control- Electricity

Did you know??

English Scientist William Sturgeon invented the first electromagnet in 1825. He wrapped a coil of wire around an iron rod and connected it to an electric circuit. The electromagnet could lift metal things. In 1829, Joseph Henry, an American, improved the idea by wrapping many layers of wire around a thick iron core. Joseph Henry’s electromagnet was powerful enough to lift one tonne! Today’s largest electromagnets, usually found in scrap yards, can easily lift a car. Electromagnets are used in many ways, from motors to scrap yards.

Activity 1: Create an Electromagnetic Field

Put a compass on the table and lay the wire across it. Wait for the compass needle to stop moving. Connect the wire to each end of the battery and watch what happens to the compass needle (Note: only connect the battery for a short time because you are making a short circuit. This drains the battery very quickly and can make the wire very hot)

Recording and Reflecting

Describe and Explain what happened to the compass needle when the battery was connected

Activity 2: Build an Electromagnet

http://www.sciencekids.co.nz/videos/physics/magnets.html

Recording and Reflecting

Did the electromagnet work? How well?

What objects do you think the electromagnet could pick up? How many could it hold at once? What would happen if you turned off the switch?

What other materials could you use for the core of the electromagnet? Would they work as well, you think? Why or why not?

Notes

Electricity and magnetism are closely related. In 1820, André Marie Ampère discovered that if you pass a current through a coil of wire, it acts just like a magnet. It has a north pole and a south pole. When the wire is wrapped around a nail, the nail becomes an electromagnet. The magnetic effect can be switched on an off.

Notes

Michael Faraday discovered that an electric current is created when a magnet is moved in and out of a wire coil.

It is now known that both electricity and magnetism are part of the same force. The force is called electromagnetism.

Notes

Electromagnets are used in motors. The inside of a motor is a coil of wire within a magnet. When the current flows through the coil, the magnets repel the coil, causing it to rotate.

Notes

Electric buzzers or bells often contain electromagnets. Inside a bell, a hammer is connected to a spring. When the switch is on, the electric current flows to the electromagnet. The electromagnet attracts the metal. The hammer hits the bell which makes a sound. As soon as the hammer moved to the bell the electric circuit is broken. This turns off the electromagnet and the hammer returns to its starting position. This process is repeated over and over again until the switch is turned off and the electric current stops flowing.

The inner workings of a bell