Electromagnetic induction
![Faraday's disk (see homopolar generator)](/Images/godic/202501/12/Faraday_disk_generator0200.jpg")
![Faraday's experiment showing induction between coils of wire: The liquid battery (right) provides a current that flows through the small coil (A), creating a magnetic field. When the coils are stationary, no current is induced. But when the small coil is moved in or out of the large coil (B), the magnetic flux through the large coil changes, inducing a current which is detected by the galvanometer (G).[12]](/Images/godic/202501/12/Induction_experiment0200.png")
![An illustration of Kelvin-Stokes theorem with surface Σ its boundary ∂Σ and orientation n set by the right-hand rule.](/Images/godic/202501/12/Stokes'_Theorem.svg0200.png")
![Rectangular wire loop rotating at angular velocity ω in radially outward pointing magnetic field B of fixed magnitude. The circuit is completed by brushes making sliding contact with top and bottom discs, which have conducting rims. This is a simplified version of the drum generator](/Images/godic/202501/12/Spindle0200.PNG")
Electromagnetic induction is the production of an electromotive force across a conductor exposed to time varying magnetic fields. Michael Faraday, who mathematically described Faraday's law of induction, is generally credited with its discovery in 1831.