Electromotive Force vs Potential Difference: Difference and Comparison

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.

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

Key Takeaways

  1. Electromotive force (EMF) is the energy source that drives current in a circuit, whereas potential difference (PD) is the energy used per unit charge.
  2. EMF is associated with voltage generation, while PD is related to the voltage drop across components in a circuit.
  3. Batteries and generators produce EMF, while PD is measured across resistors and other electrical components.

Electromotive Force vs Potential Difference

Electromotive force is independent of the resistance of the circuit and determines the difference in the terminal potential that gives rise to an electric current. The Potential difference is proportional to the resistance between two points and determines the difference in electrical potential between the points.

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 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.

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EMF occurs in a circuit with batteries or any electrical generator, and 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 the source voltage and the product (Current and internal resistance).

Numerically, it is the ratio of work done on a unit of 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 a circuit’s electric or non-electric source. On the other hand, Potential difference is the calculated amount of energy passed from one point to another in a circuit.
  2. Electromotive force is induced by electrochemical cells in the source or changes 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.
Difference Between X and Y 2023 05 05T174547.894
  1. https://ieeexplore.ieee.org/abstract/document/1191804/
  2. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA079i019p02853
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Last Updated : 14 July, 2023

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22 thoughts on “Electromotive Force vs Potential Difference: Difference and Comparison”

  1. The article provides a comprehensive overview of voltage, electromotive force, and potential difference. It’s very well-written and educational.

  2. I appreciate the historical context provided for electromotive force and potential difference. It enriches the understanding of these concepts.

  3. This explanation has been extremely helpful in clarifying the difference between electromotive force and potential difference. The article is quite informative and well-structured.

    • I couldn’t agree more! The comparison table is especially useful in understanding the key differences and similarities.

  4. The explanation of how EMF and PD are formed and their relation to circuits is exceptionally clear. Kudos to the author for presenting such intricate material so comprehensively.

  5. I found the information on the formation and measurement of EMF and PD to be very illuminating. The article handles the subject matter with great clarity.

  6. The comparison table has been a valuable addition to this article. It effectively captures the essential elements of electromotive force and potential difference.

    • The table provides a concise yet comprehensive view of the key differences and characteristics of EMF and PD. It’s an excellent resource for students and professionals alike.

  7. The direct comparison between EMF and PD has been elucidating. The article provides a deep understanding of these electrical principles.

  8. The distinctions between electromotive force and potential difference have been portrayed in a clear and methodical manner. It’s an impressive piece of technical writing.


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