Electromotive force

Electromotive force (EMF) is energy supplied per unit charge by a source or induced in a circuit. It is measured in volts, not newtons, and is not a mechanical force.

Electric potential: Electric potential is electric potential energy per unit charge at a point in an electric field. Unlike EMF, electric potential describes a location; EMF describes energy supplied around a source or circuit.
Electric charge: Electric charge is a conserved property of matter that causes electromagnetic interactions. EMF is defined by the energy transferred for each unit of charge.
Electrochemical cell: An electrochemical cell converts chemical energy into electrical energy through redox reactions. Its reactions establish the chemical EMF that drives charge through a circuit.
Mechanical force: Mechanical force is an interaction that changes an object's motion or shape, measured in newtons. Despite its name, electromotive force is energy per charge, not a mechanical force.
Electromagnetic induction: Electromagnetic induction is the production of an electromotive force by changing magnetic flux through a circuit. Changing magnetic flux generates EMF even without a battery or other chemical source.
Voltage: Voltage is the difference in electric potential between two points. EMF is often called a source's voltage, though the terms describe different physical quantities.
Electric generator: An electric generator converts mechanical energy into electrical energy by electromagnetic induction. Generators produce EMF as their coils and magnetic fields move relative to one another.
Electromotive force and terminal voltage: Electromotive force and terminal voltage are distinct source quantities, related by internal voltage drops under load. Their difference under load is central to interpreting measurements of a real source.
Faraday's law of induction: Faraday's law relates induced electromotive force to the rate of change of magnetic flux. It quantifies the induced EMF that changing flux produces.
Electric current: Electric current is the rate at which electric charge passes a point. Current flows when a source's EMF drives charge through a closed circuit.

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