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The electromotive force generated by motion is often referred to as motional emf. When the change in flux linkage arises from a change in the magnetic field around the stationary conductor, the emf is dynamically induced. The electromotive force generated by a time-varying magnetic field is often referred to as transformer emf.
The science of electric fields, magnetic fields, currents, charges, and forces. electromechanical A system that has both an electrical component and a mechanical component, such as a motor or a relay. electromote An 1882 demonstration of a prototype electric trolley bus. electromotive force
The current induced in a circuit due to a change in a magnetic field is directed to oppose the change in flux and to exert a mechanical force which opposes the motion. Lenz's law is contained in the rigorous treatment of Faraday's law of induction (the magnitude of EMF induced in a coil is proportional to the rate of change of the magnetic flux ...
That is, the back-EMF is also due to inductance and Faraday's law, but occurs even when the motor current is not changing, and arises from the geometric considerations of an armature spinning in a magnetic field. This voltage is in series with and opposes the original applied voltage and is called "back-electromotive force" (by Lenz's law).
The inverse relationship between force per unit current and of a linear motor has been demonstrated. To translate this model to a rotating motor, one can simply attribute an arbitrary diameter to the motor armature e.g. 2 m and assume for simplicity that all force is applied at the outer perimeter of the rotor, giving 1 m of leverage.
The SI unit of work per unit charge is the joule per coulomb, where 1 volt = 1 joule (of work) per 1 coulomb of charge. [citation needed] The old SI definition for volt used power and current; starting in 1990, the quantum Hall and Josephson effect were used, [10] and in 2019 physical constants were given defined values for the definition of all SI units.
The volt (symbol: V) is the unit of electric potential, electric potential difference , and electromotive force in the International System of Units (SI). [ 1 ] Definition
Symbol [1] Name of quantity Unit name Symbol Base units E energy: joule: J = C⋅V = W⋅s kg⋅m 2 ⋅s −2: Q electric charge: coulomb: C A⋅s I electric current: ampere