Electromagnetic InductionThe phenomenon called electromagnetic induction was first noticed and studied by Michael Faraday, in 1831. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a variable magnetic field on the conductor and is a very important concept. Faraday discovered that whenever the magnetic field around an electromagnet was made to grow and collapse by closing and opening the electrical circuit of which it was a part, an electric current could be detected in a separate conductor nearby. Faraday also studied the possibility that a current could be produced by a magnetic field placed near a coiled wire. Simply placing the magnet near the wire could not produce current. Faraday discovered that in this situation a current could only be produced if the magnet had a certain speed. The magnet could be moved in a positive or negative direction, but it had to be moving to produce current in the wire. The current in the coil is called an induced current, because the current is caused (or “induced”) by a changing magnetic field (Cutnell and Johnson 705). The induced current is supported by an emf. Since an emf source is always required to produce current, the coil itself behaves as if it were an emf source. The emf is known as induced emf. Therefore, a changing magnetic field induces an emf in the coil, and the emf leads to an induced current (705). He also found that moving a conductor near a stationary permanent magnet caused current to flow in the wire as long as it moved as in the coiled magnet and wire configuration. Faraday visualized a magnetic field as composed of many lines of induction, along which a small magnetic compass would point. The set of lines that intersect a given area is called magnetic flux. Faraday attributed the electrical effects to changing magnetic flux. The need for movement to produce a current is due to the fact that electromagnetic induction involves a time-varying magnetic field. The same effects can be produced by moving the coil towards and away from an immobile magnetic source. In both cases, the key to producing the current is certainly the movement of the magnet or wire. The magnetic lines of the magnetic field must pass through a loop of the spiral wire.