Day 127

Electromagnetism History -1800’s

  • The Industrial Revolution used machines powered by water or steam.
  • As the revolution progressed, electrical machines became increasingly popular.
  • Voltaic cells were the original devices capable of generating the electromotive force (emf).
  • The voltaic cells did not generate much electric power and were soon to be replaced.

Unexpected Classroom Results

  • In 1820, a Dutch physicist, Hans Christian Oersted, was demonstrating to his students that electricity and magnetism were NOT related.
  • Much to his surprise, when he closed the circuit of his demonstration apparatus, the needle on his compass needle moved indicating a magnetic field around the current-carrying wire.

First Electromagnet

  • In 1825, William Sturgeon, an English inventor, developed the first electromagnet The electromagnet consists of a soft-iron core magnetized by passing a current through a wire wound around the core.

Strength of Electromagnet

  • The strength of an electromagnet can be increased by increasing the:
  • Number of turns of the wire
  • Amount of current flowing through the wire
  • Permeability of the core (iron has a high permeability – or good capacity to increase magnetic flux) Would an air coil make a stronger or weaker electromagnet?

Ampere’s Rule for a Solenoid

  • An electromagnet is actually a solenoid.
  • The rule states when grasping the coil in your left hand so that your fingers circle the coil in the direction of the current, your thumb will point to the North pole of the core.
  • Remember that electrons flow from negative to positive electrodes. The N end of a compass will point to the S end of a solenoid since opposites attract.

Electromagnetism – Discovery

  • Michael Faraday and Joseph Henry, scientists, discovered that electric current can be produced by changing the magnetic field in a conductor. This became known as electromagnetic induction.

Electromagnetism History – 1900’s

  • Principles of electromagnetism were discovered and the electric generator was developed. The generator revamped the Industrial Revolution.
  • Electric motors were soon to follow.