http://www.ck12.org Chapter 25. Electromagnetism
FIGURE 25.1
Hans Christian Oersted was the scientist who discovered electromag-
netism.FIGURE 25.2
In Oersted’s investigation, the pointer of the magnet moved continuously
as it circled the wire.Electric Currents and Magnetic Fields
The magnetic field created by a current flowing through a wire actually surrounds the wire in concentric circles.
This magnetic field is stronger if more current is flowing through the wire. The direction of the magnetic field also
depends on the direction that the current is flowing through the wire. A simple rule, called the right hand rule, makes
it easy to find the direction of the magnetic field if the direction of the current is known. The right hand rule is
illustrated inFigure25.3. When the thumb of the right hand is pointing in the same direction as the current, the
fingers of the right hand curl around the wire in the direction of the magnetic field. You can see the right hand rule
in action at this URL: http://www.youtube.com/watch?v=eK1Ar5WPJj8.
Lesson Summary
- Electromagnetism is magnetism produced by an electric current. Electromagnetism was discovered by Oersted
in 1820. - The magnetic field produced by a current in a wire moves around the wire in concentric circles. More current
creates a stronger magnetic field, and the direction of the current determines the direction of the magnetic
field.