The electromotive force shows the amount of energy given to each coulomb of charge. On the other hand, the potential difference shows the amount of energy utilized by one coulomb of charge.
Electromotive Force (EMF) and Potential Difference are two important quantities in an electrical or electronic circuit. E.M.F and Potential Difference both are used to deliver energy to the circuit in two different ways. While E.M.F is the voltage generated at the terminals of the battery, Potential difference is the voltage generated between any two points of the electric circuit.
In this article, we will discuss major differences between electromotive force (E.M.F) and potential differences along with a general understanding of the two forms of energy.
What is Electromotive Force?
Electromotive Force also called E.M.F, is defined as the energy exerted on a single unit of charge in coulombs. In other words, E.M.F is the voltage drop produced at the ends of a battery or a cell. Electromotive force is produced as a result of the chemical reaction taking place inside the battery, which in turn generates an electric current. The emf is represented by the symbol E. If work done in moving a unit charge (q) in coulombs from the positive end to the negative end of the battery/cell is W, then the expression for emf is given by:
What is Potential Difference?
Potential Difference (P. D.) is also called voltage. It is defined as the energy consumed by a unit of charge from the source which it carries from one point to another in an electric circuit. The idea of the potential difference comes from Ohm’s law, according to which the potential difference is defined as the product of the amount of current flowing across two given points and the resistance offered to the current flowing through the conductor. The potential difference across two given points is given by the following expression:
Where,
V is the potential difference, I is current, and R is the resistance.
Difference between Electromotive Force and Potential Difference
Although the Electromotive force and Potential difference could be considered as different terms of voltage, they have some significant differences between them. Some of the major differences between them are listed in the following table.
| Parameter | Electromotive Force | Potential Difference |
| Definition | Electromotive force is defined as the total amount of energy and voltage generated by the terminals of a battery or any other non-electrical source. | Potential difference is defined as the amount of energy utilized by a unit charge to move between two given points in a circuit. |
| Discovery | The English scientist, Michael Faraday introduces the concept of emf by performing an experiment on electrode-electrolyte reaction across the voltaic cell. | The concept of Potential difference generated between two given points was brought to light by the German scientist Georg Simon Ohm, through the Ohms law. |
| Cause | Electromotive force is generated by the electrochemical reaction taking place inside the battery or electric source. It is also caused by any changes in the magnetic flux around the circuit. | Potential difference is caused by the flow of current due to the voltage generated by the source in the circuit. The Motion of the electrons in the circuit across two given points creates a potential difference. |
| Abbreviation | The shot hand representation of electromotive force is emf. | The shot hand representation of electromotive force is P.D. |
| Symbol representation | EMF is represented by the symbol E. | Potential difference is represented by the symbol V. |
| Unit of measurement | The SI unit of measurement of electromotive force is the volt. | The SI unit of measurement of potential difference is also a volt. |
| Formula | EMF is given by the following formula, E= Work done(W)/Charge(q) | Potential difference is given by, V=IR |
| Source of generation | The source of generation of emf is a battery or rotating generator (dynamo). | The source of generation of P.D. is a battery or any source of emf. |
| Dependence on resistance | EMF is not dependent on the resistance offered by the circuit. | Potential difference is directly proportional to the resistance offered by the circuit. |
| Variance | EMF has a fixed magnitude which does not vary with any change in current. | Potential difference is not constant and keeps varying depending on the intensity of the current flow. |
| Value of voltage | EMF is the total or maximum voltage produced by the electric source in the circuit. | The value of the potential difference is less than the total voltage or emf produced by the battery source in the circuit. |
| Type of field | EMF is generated by magnetic and electric fields. | Potential difference is produced by the electric field (flowing current) only. |
| Measuring tool | EMF is measured using the EMF meter. | P.D. is measured using the voltmeter. |
| Applications | EMF measurement finds its applications in determining the PH of a solution, the valency of electrons produced in the electric circuit, Gibb’s free energy, the equilibrium constant of a cell, etc. | Measurement of Potential difference finds applications in audio control, televisions, transducers, measuring instruments, etc. |
Conclusion
In conclusion, Electromotive force and Potential difference are two different parameters of voltage. But there exist some significant differences between them. The major criteria of difference between them are that Electromotive force is produced at the terminals of a battery and it is the net voltage applied across the entire circuit. On the other hand, the potential difference is the voltage generated from the movement of electrons or electronic charge of value 1 coulomb between two given points in an electric circuit. But together both emf and potential difference are important parameters that determine the overall operation and functioning of an electronic circuit that also finds a wide variety of commercial applications.