When current flows through a conductor, a field of magnetic energy is created around that conductor as a byproduct of energy transmission. These fields are identical in nature to the fields surrounding a natural magnet, but unlike magnets, which have permanent magnetic fields, EMFs are only produced in the presence of flowing current. In some devices, EMFs are desirable, but EMFs in electrical energy production are considered an unavoidable side effect from the production and transmission process.

Energy used to create an EMF is energy which is lost to the electrical current flowing through the conductor. Typically the strength of the magnetic field is in direct proportion to the quality of the conductor. The more efficiently it carries current, the less transmission loss it suffers to EMF radiation, and the weaker the field.

EMF has often been used to denote the field itself, but more commonly it refers to the specific type of radiation produced by these fields (EMF radiation). Most devices that consume electricity, and some devices that do not consume electricity but use electrical principles in their operations, are capable of producing varying levels of EMF radiation.

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