# Difference Between EMF and Voltage

Last Updated on January 3, 2024 by Electricalvolt

The fundamental difference between EMF and voltage is related to the voltage magnitude present at the terminals of a source when there is no current flow, as opposed to the voltage magnitude at the source’s end when current flows through the circuit.

In other words, EMF represents the maximum potential difference between any two points in a circuit, which is generated by a source when an electrical load does not draw current. In comparison, voltage represents the potential difference between two specific points in the circuit. It is important to note that the resistance of the circuit does not influence the EMF and represents the pure voltage output by the source. On the other hand, voltage is influenced by the resistance of the circuit, and its magnitude decreases as the current flows through the circuit.

## What is EMF?

Electromotive force (EMF) is a phenomenon that arises when energy is expended in the form of chemical, mechanical, or light to separate electrons from atoms, resulting in the formation of electrically charged particles. EMF can be generated by an electrochemical cell or by changing the magnetic field.

The unit of measurement for EMF is volts, which is symbolized by the letter E. It is important to note that EMF is a fundamental concept in electrical engineering and physics and plays a significant role in many applications, including power generation and transmission, electric motors, and electronic circuits.

In the context of an ideal power source, it is important to note that the voltage across the terminals of said source, when no current is being drawn from it, is equal to its EMF (electromotive force). This relationship is illustrated in the circuit below.

## What is Voltage?

The concept of voltage refers to the difference in electrical charge between two points. Electrons migrate from the negatively charged pole to the positively charged pole of a closed electrical circuit. Voltage is the measure of the electric force’s work in transporting a charge from one point to another within an electric field. The unit of measurement for voltage is the volt (V), and it is expressed in the International System of Units (SI).

When you have a circuit like the one shown below, the voltage at the ends of the power source is the same as the voltage across the load when the power source supplies the current.

### Formula for Voltage

The voltage can be defined as the amount of work done per unit charge. The formula is given below.

## Difference Between EMF and Voltage

### Sample Problems

Problem 1: A battery with an internal resistance of 0.1 ohms produces a potential difference of 4.3 volts when supplying 0.5 amperes of current. Determine its EMF.

Given Data-
V=4.3V
I= 0.5 A
r=0.1 Ohms

Solution:

Problem 2: Given a battery with a terminal voltage of 3 volts and an internal resistance of 0.02 ohms, what is the current being supplied to a load with a resistance of 0.7 ohms?

Given Data-
V= 3 Volts
r=0.02 Ohms
R= 0.7 Ohms

Solution:

## Conclusion:

In conclusion, it is crucial to understand the difference between EMF and voltage in electrical systems and circuits. Although both terms are often used interchangeably, they represent distinct concepts.