Electromagnetic Induction

Faraday's electromagnetic induction experiment
Faraday's electromagnetic induction experiment, 1882. The inner coil is connected to a liquid battery, the outer coil to a galvanometer. Michael Faraday (1791-1867) was one of the greatest scientists of the 19th century. His most significant contribution was the Experimental Researches on Electricity which was published over 40 years, where he described his discoveries, including the laws of electromagnetic induction (1831) and the laws of electrolysis (1833). He also discovered the principles of the electric motor and dynamo. Oxford Science Archive/Print Collector/Getty Images

Electromagnetic induction (or sometimes just induction) is a process where a conductor placed in a changing magnetic field (or a conductor moving through a stationary magnetic field) causes the production of a voltage across the conductor. This process of electromagnetic induction, in turn, causes an electrical current - it is said to induce the current.

Discovery of Electromagnetic Induction

Michael Faraday is given credit for the discovery of electromagnetic induction in 1831, though some others had noted similar behavior in the years prior to this.

The formal name for the physics equation that defines the behavior of an induced electromagnetic field from the magnetic flux (change in a magnetic field) is Faraday's law of electromagnetic induction.

The process of electromagnetic induction works in reverse as well, so that a moving electrical charge generates a magnetic field. In fact, a traditional magnet is the result of the individual motion of the electrons within the individual atoms of the magnet, aligned so that the generated magnetic field is in a uniform direction. (In non-magnetic materials, the electrons move in such a way that the individual magnetic fields point in different directions, so they cancel each other out and the net magnetic field generated is negligible.)

Maxwell-Faraday Equation

The more generalized equation is one of Maxwell's equations, called the Maxwell-Faraday equation, which defines the relationship between changes in electrical fields and magnetic fields.

It takes the form of:

∇×E = – B / ∂t

where the ∇× notation is known as the curl operation, the E is the electric field (a vector quantity) and B is the magnetic field (also a vector quantity). The symbols ∂ represent the partial differentials, so the right-hand of the equation is the negative partial differential of the magnetic field with respect to time.

Both E and B are changing in terms of time t, and since they are moving the position of the fields are also changing.

Also Known As: induction (not to be confused with inductive reasoning), Faraday's law of electromagnetic induction