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Difference Between EMF and Voltage

Dyson

08/01/2025

One of the key differences between electromotive force (EMF) and voltage is that EMF refers to the energy supplied to charges, while voltage represents the energy required to move a unit charge from one point to another. Other distinctions between the two are detailed in the comparison chart below.

Comparison Chart

Definition of Voltage

Voltage is defined as the energy required to move a unit charge from one point to another. It is measured in volts (V) and denoted by the symbol

V

. Voltage is induced by electric and magnetic fields.

Voltage is generated between the two terminals of a source (i.e., the cathode and anode). The potential at the positive terminal of the source is higher than that at the negative terminal. When voltage is developed across a passive component in a circuit, it is referred to as a voltage drop. According to Kirchhoff’s law, the sum of all voltage drops in a circuit equals the electromotive force (EMF) of the source.

Definition of EMF

Electromotive force (EMF) is the energy supplied by a source to each coulomb of charge. In other words, it is the energy provided by an active source (such as a battery) per unit coulomb of charge. EMF is measured in volts (V) and denoted by the symbol ε.

The electromotive force of the above circuit is represented by the formula

Where, r – internal resistance of the circuit.

R – External resistane of the circuit.
E – electromotive force.
I – current

Key Differences Between EMF and Voltage

EMF (electromotive force) measures the energy supplied to each coulomb of charge, while voltage measures the energy consumed by one coulomb of charge to move from one point to another.
EMF is denoted by the symbol ε, whereas voltage is represented by $V$ .
EMF is measured across the terminals of a source when no current flows through it, while voltage is measured between any two points in a closed circuit.
EMF is generated by active sources such as electrochemical cells, dynamos, and photodiodes; voltage, on the other hand, is induced by electric and magnetic fields.

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Basic Physics Articles

Dyson

Focused on the design of electrical equipment, proficient in electrical principles and relevant specifications, and skilled in using design software. From intelligent substations to various types of electrical equipment, I am adept at optimizing design solutions, integrating new technologies. With practical experience and collaborative management capabilities, I deliver outstanding electrical design achievements.

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