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electromotive force
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   Also found in: Dictionary/thesaurus, Medical, Financial, Acronyms, Encyclopedia, Wikipedia 0.06 sec.

electromotive force

In physics, the energy supplied by a source of electric power in driving a unit charge around the circuit. The unit is the volt. The term is therefore used to describe the voltage produced by an electric battery or generator in an electrical circuit.

A difference in charge between two points in a material can be created when an external energy source such as a battery causes electrons to move so that there is an excess of electrons at one point and a deficiency at a second point. This difference in charge gives rise to electrical potential energy known as emf. It is the emf that causes a current to flow through a circuit.

When the source is connected in a circuit some of the energy it supplies will be lost in driving current across its own internal resistance, and so its terminal voltage (the potential difference across its terminals) will be less than its emf. If a source's terminal voltage is V volts, the current it supplies to a circuit I amperes, and its internal resistance r ohms, then its emf E can be expressed as: E = V + Ir or, where R is the total circuit resistance, as: E = I(R + r)



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? Mentioned in ? References in periodicals archive
 
The precautionary principle and risk perception: experimental studies in the EMF area.
It found that the 20,400 Stockholm-area women who developed breast cancer over a 23-year period had no higher EMF exposures than did 116,000 cancerfree women from that region.
reports have concluded that limited evidence exists for an association between EMF (electromotive force) exposure and increased leukemia risk but that when all the scientific evidence is considered, the link between EMF exposure and cancer is weak.
 
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