How Electromagnetic Induction Creates Current

Faraday's electromagnetic induction experiment, including many cylinders, tubes, and weirs, in illustrated form

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Electromagnetic induction (also known as Faraday's law of electromagnetic induction or just induction, but not to be confused with inductive reasoning), 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.

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Jones, Andrew Zimmerman. "How Electromagnetic Induction Creates Current." ThoughtCo, Aug. 27, 2020, Jones, Andrew Zimmerman. (2020, August 27). How Electromagnetic Induction Creates Current. Retrieved from Jones, Andrew Zimmerman. "How Electromagnetic Induction Creates Current." ThoughtCo. (accessed March 5, 2021).