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
- Electromotive force (EMF) is the energy source that drives current in a circuit, whereas potential difference (PD) is the energy used per unit charge.
- EMF is associated with voltage generation, while PD is related to the voltage drop across components in a circuit.
- 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 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 Comparison | Electromotive 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). |
| History | In 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. |
| Formula | E=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, 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.
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.
Main Differences Between Electromotive Force and Potential Difference
- 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.
- 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.
- 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.
- The Electromotive Force formula is Work/ Charge (EMF=W/Q). Notwithstanding, the Potential formula is derived as Voltage=Current x Resistance (V=IR).
- 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.
- https://ieeexplore.ieee.org/abstract/document/1191804/
- https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA079i019p02853
Last Updated : 14 July, 2023
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
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