E LECTROMAGNETISM Section 1: What is Electromagnetism?

W HAT IS ELECTROMAGNETISM ? (1820) Hans Christian Oersted produced a current in a wire during a lecture. When he brought a compass near the wire, the compass changed direction. Whenever he turned on the current in the wire, the compass needles lined up around the write in the shape of a circle.

E LECTRIC C URRENT & M AGNETISM How can you observe electromagnetism? Compass & electric current A compass needle normally points north because it aligns itself with Earth’s magnetic field The needles of compasses surrounding a current will align with the current, producing a circle

E LECTRIC C URRENT & M AGNETISM Wherever there is electricity, there is magnetism An electric current produces a magnetic field This relationship is called electromagnetism

W HAT DO THEY LOOK LIKE ? An electromagnets can be made out of a variety of materials but they all have the following: Voltage source (battery or other source) A magnetic core Wire wrapped around the core. This is known as a solenoid. The more times the wire is wrapped around the core the greater the strength of the magnet.

T HE M AGNETIC F IELD The magnetic field produced by a current has three distinct characteristics: 1. The field can be turned on and off 2. The field can have its direction reversed 3. The field can have its strength changed

T HE M AGNETIC F IELD You can turn a magnetic field produced by a current on and off… How can you turn the magnetic field off? Simply by turning the current off!

T HE M AGNETIC F IELD You can change the direction of a magnetic field… How can you change the direction? Simply by reversing the direction of the current!

S OLENOIDS You can change the strength of a magnetic field produced by a current… How can you change the strength? Simply by looping, or winding, the wire of the wire! The strength will increase as the number of loops or coils increases A solenoid is a coil of wire with a current.

E LECTROMAGNETS A solenoid with a ferromagnetic core is called an electromagnet. The magnetic field of an electromagnet can be hundreds or thousands of times stronger than the magnetic field of the current alone Basically, an electromagnet is a strong magnet that can be turned on or off.

E LECTROMAGNETS You can increase the strength of an electromagnetic field… 1. Increase the current in the solenoid 2. Add more loops of wire to the solenoid 3. Wind the coils of the solenoid closer together 4. Increase the strength of an electromagnet by using a stronger ferromagnetic material for the core

C OMMON E LECTROMAGNETS Audiotapes Videotapes Computer hard drives Credit cards Doorbells Radios Refrigerators