Electromagnets Mrs. V 2015

How was electromagnetism discovered? *Hans Christian Oersted discovered electromagnetism by accident! *He touched a wire that had a current flowing through it to a compass. The needle no longer pointed North!

Demonstration of Oersted’s Experiment:

He also discovered that… The direction of the magnetic field depends on the direction of the current. Another scientist Jean- Marie Ampere heard about this work, and electromagnetism was born!

Solenoids A solenoid is a coil of wire that produces a magnetic field when an electric current runs through it. A solenoid gets stronger two ways: The more loops it has, the stronger it gets The more current that flows through the wire, the stronger it gets

Even Stronger… We can make electromagnets that are even stronger than a solenoid. This is called an ELECTROMAGNET. It is a solenoid wrapped around an iron core.

How does it work? The magnetic field of the solenoidlines up the domains of the iron nail. Therefore, the magnetic field of the electromagnet is the magnetic field of the solenoid PLUS the magnetic field of the iron core

What are electromagnets used for?

Electromagnets can be turned on and off! They can be used to pick up things and let them go, like the junkyard magnet in the previous slide

Doorbells 1. Press button 2. Magnetic field drops, light goes out 3. The change in the field causes a current in the second solenoid 4. This current induces a magnetic field that pushes an iron rod and makes the bell ring.

The circuit for a door bells includes an electromagnet.

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Multiple-choice quiz