In 1820, Hans Christian Oersted observed that electric currents create magnetic fields. Consequently many scientists made unsuccessful attempts to create current in the presence of magnetic fields. After over 10 years of investigation Michael Faraday and Joseph Henry, working independently on different sides of the Atlantic, made the discovery that if a conducting coil has a changing magnetic flux passing through it an electromotive force is created that causes a current to flow through the coil. The equation describing this phenomenon quantitatively is known as Faraday’s Law.


In this activity, you will

  • Use Faraday’s Law to explain why the current induced in a coil (and thus the voltage) across it changes the way it does when the north or south pole of a rod shaped magnet is moved into and then back out of the center of a coil of wire at various speeds.