Search results
Results from the WOW.Com Content Network
However, electromotive force itself is not a physical force, [5] and ISO/IEC standards have deprecated the term in favor of source voltage or source tension instead (denoted ). [ 6 ] [ 7 ] An electronic–hydraulic analogy may view emf as the mechanical work done to water by a pump , which results in a pressure difference (analogous to voltage) .
The electrostatic field causes separation of these pairs, establishing an electromotive force in the process. The electric field sends the electron to the p-type material, and the hole to the n-type material. If an external current path is provided, electrical energy will be available to do work.
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 ...
An active network contains at least one voltage source or current source that can supply energy to the network indefinitely. A passive network does not contain an active source. An active network contains one or more sources of electromotive force. Practical examples of such sources include a battery or a generator. Active elements can inject ...
The term electromotive force was first used by Volta in a letter to Giovanni Aldini in 1798, and first appeared in a published paper in 1801 in Annales de chimie et de physique. [25]: 408 Volta meant by this a force that was not an electrostatic force, specifically, an electrochemical force.
The term back electromotive force is also commonly used to refer to the voltage that occurs in electric motors where there is relative motion between the armature and the magnetic field produced by the motor's field coils or permanent magnet field, thus also acting as a generator while running as a motor. This effect is not due to the motor's ...
In general, the Seebeck effect is described locally by the creation of an electromotive field E emf = − S ∇ T , {\displaystyle \mathbf {E} _{\text{emf}}=-S\nabla T,} where S {\displaystyle S} is the Seebeck coefficient (also known as thermopower), a property of the local material, and ∇ T {\displaystyle \nabla T} is the temperature gradient.
Faraday's law states that the emf is also given by the rate of change of the magnetic flux: =, where is the electromotive force (emf) and Φ B is the magnetic flux. The direction of the electromotive force is given by Lenz's law.