Difference Between Electromotive Force and Potential Difference

Voltage has different types of terms. As if electromotive force and potential difference are a part of this type. In the abstract, voltage is the pressure produced in an electrical circuit’s power source that shoves charged electrons through a conductor, thereby causing current.


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However, all the concepts subordinate to voltage have the same use, which is to cause the flow of current in an electrical circuit. 

Electromotive Force vs Potential Difference

The difference between electromotive force and the potential difference is that the electromotive force (emf) is the energy per unit charge exerted by the energy source throughout the circuit. While the potential difference (P.D) is the energy released when the current flows from one point to another in the circuit. 

Electromotive Force vs Potential Difference

Electromotive force is not a type of force but an electrical action produced by a non-electrical source. Furthermore, emf is the electric potential caused by a magnetic field as well as an electrochemical cell.

The measure of emf is the work done on a unit electric charge. It is represented by ε, and the SI unit is Volts (V).

On the other hand, the Potential difference is the difference calculated in the amount of energy that the charge carries from one point to another in the circuit. However, it is often denoted as the voltage. It is represented by P.D, and the SI unit is Volts(V). 

Comparison Table

Parameters of ComparisonElectromotive Force Potential Difference
Meaning Electromotive force is the energy per unit charge created by an electrical or non-electrical source in a circuit. It is denoted as Ɛ and its SI unit is Volts (V). Potential Difference is the amount of energy that is calculated as the difference between one point and another in a circuit. The potential difference is denoted as P.D and its SI unit is Volts (V). 
HistoryIn the 1830s, Michael Faraday established the new chemical reaction, where two electrode-electrolyte formed EMF for the voltaic cell.Potential differences defined after the theory of Alessandro Volta had been proved. 
Caused Electromotive force may be caused by electrochemical cells or any changes in the magnetic field.Potential difference engenders when the current flows through the conductor, where free electrons move around and ultimately cause potential difference from one point to another.
FormulaE=W/QElectromotive force= Work (Divide) Charge. V=IRVoltage= Current (Multiple) Resistance.
Formation Electromotive force forms either by electrochemical cell or magnetic field. Besides, EMF may form even without current flow in a circuit. Potential Difference forms only in an electric field. 

What is Electromotive Force?

Thus, Electromotive force (EMF) is kinda related to voltage, but it is the energy per unit charge imparted by an electrical source, such as a battery or an electrical generator. It is not at all a force concept but an electrical potential generated by an electrochemical cell or a changing magnetic field.

EMF occurs in a circuit with batteries or any electrical generator, as in this, one terminal is positively charged while the latter is negatively charged. Subsequently, the current will be flown due to the potentially charged electrodes. It is represented as ε, and the SI unit is Volts. 

Besides, the Faraday law relates emf in the first by stating that the development of the electromagnetic field is due to the induced emf. The measure of Emf is the sum of source voltage and the product (Current and internal resistance).

Numerically, it is the ratio of work done on a unit electric charge in the whole circuit. However, the value of emf is constant throughout the circuit. 

electromotive force

What is Potential Difference? 

On the contrary, the potential difference is actually the voltage difference between the two points in a circuit. In simple words, it is the electric energy transferred from one point to another in a circuit.

When current flows through a conductor, the free electrons tend to move around, and this movement causes a difference in energy across the component, which is called an electrical potential difference. 

However, the PD is not constant, as it determines the measure of energy between any two points of the circuit. It is represented as P.D with the SI unit Volts.

The value of the potential difference is calculated by relating Ohm’s Law, where the potential difference is equal to the product of the current and resistance of the circuit.

Additionally, it can also be determined by a device called the voltmeter. Following the EMF’s part in the gravitational field, electric and magnetic fields, Potential difference is elicited only with the presence of electric fields. 

potential difference

Main Differences Between Electromotive Force and Potential Difference

  1. Electromotive force is the energy per unit charge attained through an electric or non-electric source in a circuit. On the other hand, Potential difference is the calculated difference amount of energy passed from one point to another point in a circuit.
  2. Electromotive force is induced either by electrochemical cells in the source, or changes occurred in the magnetic field. Whereas, Potential Difference is caused by the free-electron travel through the conductor between two points. 
  3. The electromotive force was derived by Michael Faraday in 1830, after analysing the chemical reaction of two electrodes and electrolytes. While Potential Difference is defined after the success rate of Alessandro Volta’s theory.
  4. The Electromotive Force formula is Work/ Charge (EMF=W/Q). Notwithstanding, the Potential formula is derived as Voltage=Current x Resistance (V=IR).
  5. Electromotive force forms through non-electrical sources as well as electrical sources by staging as a constant in the circuit. But, the Potential Difference is appeared only in an electrical source and varies according to the amount of energy passed through.


  1. https://ieeexplore.ieee.org/abstract/document/1191804/
  2. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA079i019p02853
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