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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.
Eddy currents occur when a solid metallic mass is rotated in a magnetic field, because the outer portion of the metal cuts more magnetic lines of force than the inner portion; hence the induced electromotive force is not uniform; this tends to cause electric currents between the points of greatest and least potential. Eddy currents consume a ...
By 1873, the British Association for the Advancement of Science had defined the volt, ohm, and farad. [12] In 1881, the International Electrical Congress, now the International Electrotechnical Commission (IEC), approved the volt as the unit for electromotive force. [13]
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 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
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
The direction of the electromotive force is given by Lenz's law. The laws of induction of electric currents in mathematical form were established by Franz Ernst Neumann in 1845. [21] Faraday's law contains the information about the relationships between both the magnitudes and the directions of its variables.
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.