Electromagnetism - cpb-us-e1.wpmucdn.com · What is electromagnetism? (1820) Hans Christian Oersted produced a current in a wire during a lecture. When he brought a compass near the

Electromagnetism

Section 1: What is Electromagnetism?

What 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.

Electric Current & Magnetism

Wherever there is electricity, there is magnetism

An electric current produces a magnetic field

This relationship is called electromagnetism

Electric Current & Magnetism

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

The Magnetic Field

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

The Magnetic Field

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!

The Magnetic Field

You can change the direction of a magnetic field…

How can you change the direction?

Simply by reversing the direction of the current!

Solenoids

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.

Electromagnets

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.

Electromagnets

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

Common Electromagnets

Audiotapes

Videotapes

Computer hard drives

Credit cards

Doorbells

Radios

Refrigerators

Video Questions http://videos.howstuffworks.com/search.php?media=video&terms=electromagnet

1. Did the electromagnetic watch have an affect on the bullet?

2. What happened when the Mythbusters Crew increased the magnets?

3. How many degrees did the turkey increase?

4. What caused this increase?