Difference Between EMF and Voltage

The basic difference emf and voltage is that magnitude of electromagnetic force (EMF) varies with alterations in the magnetic field, while voltage is contingent on both the current’s strength and the resistance. Voltage denotes the contrast in electrical potential between two points.

What is EMF?

Electromotive force, often abbreviated as EMF, serves as the energy source for charging through a battery cell. Essentially, it establishes and sustains a voltage within the active cell by providing energy in Joules per Coulomb of charge. Denoted by “ε” and measured in volts, EMF is the maximum potential difference between two points of the battery when no current flows, as in the case of an open circuit.

This phenomenon is generated by the EMF and is influenced by voltage or potential difference. Whether from a generator or a battery, these devices convert one form of energy into another. Within such devices, one terminal carries a positive charge while the other bears a negative charge, thus EMF represents the work done on a unit electric charge.

What is Voltage?

Voltage is characterized as the energy needed to transport unit charge from one point to another. It is quantified in volts and denoted by the symbol V. Voltage arises due to both the electric and magnetic fields.

Between the terminals (such as the cathode and anode) of a source, a voltage is established. The positive terminal of the source has a higher potential compared to the negative terminal. When voltage occurs across a passive element, it is termed as voltage drops. According to Kirchoff’s law, the cumulative sum of voltage drops in a circuit equals the electromotive force (EMF).

EMF vs Voltage

The primary difference between emf and voltage is given below:

AspectElectromotive Force (EMF)Voltage
DefinitionRepresents the voltage generated within the source.Denotes the potential difference between two points..
CauseProduced by external forces inside the electric source.Arises from work done moving charge within a wire.
FormulaE = I * (R + r)V = I * R
Force OperationFollows the coulomb force operation.Follows a non-coulomb force operation.
MeasurementMeasured with an EMF meter.Measured with a voltmeter.
Relation to VoltageAlways greater than voltage.Always lesser than EMF.
IntensityIntensity remains constant.Intensity may vary.
Field InfluenceCaused in gravitational, electric, or magnetic fields.Caused only in the electric field.

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