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For a circuit using a battery source, the emf is due solely to the chemical forces in the battery. For a circuit using an electric generator, the emf is due solely to a time-varying magnetic forces within the generator. Both a 1 volt emf and a 1 volt potential difference correspond to 1 joule per coulomb of charge.
Position vector r is a point to calculate the electric field; r ... Electromotive force (emf), voltage across entire circuit including power supply, ...
Faraday's law of induction (or simply Faraday's law) is a law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (emf). This phenomenon, known as electromagnetic induction , is the fundamental operating principle of transformers , inductors , and many types of electric ...
This change in magnetic flux, in turn, induces a circular electromotive force (EMF) in the sheet, in accordance with Faraday's law of induction, exerting a force on the electrons in the sheet, causing a counterclockwise circular current in the sheet. This is an eddy current.
The emf generated by Faraday's law of induction due to relative movement of a circuit and a magnetic field is the phenomenon underlying electrical generators. When a permanent magnet is moved relative to a conductor, or vice versa, an electromotive force is created.
where is back EMF, is the constant, is the flux, and is the angular velocity. By Lenz's law, a running motor generates a back-EMF proportional to the speed. Once the motor's rotational velocity is such that the back-EMF is equal to the battery voltage (also called DC line voltage), the motor reaches its limit speed.
Electric field from positive to negative charges. Gauss's law describes the relationship between an electric field and electric charges: an electric field points away from positive charges and towards negative charges, and the net outflow of the electric field through a closed surface is proportional to the enclosed charge, including bound charge due to polarization of material.
The two equations for the EMF are, firstly, the work per unit charge done against the Lorentz force in moving a test charge around the (possibly moving) surface boundary ∂Σ and, secondly, as the change of magnetic flux through the open surface Σ. This equation is the principle behind an electrical generator.