Difference Between Electromotive Force & Potential Difference

The potential difference and electromotive force (emf) both is the form of energy. One of the major difference between the emf and potential difference is that the emf is caused by converting the other form of energy into electrical energy whereas in potential difference the electrical energy is converted into other forms of energy. Some other differences between them are explained below in the form of the comparison chart.

Content: Electromotive Force V/s Potential Difference

1. Comparison Chart
2. Definition
3. Key Differences
4. Point to Remember

Comparison Chart

Basis For Comparison	Electromotive Force	Potential Difference
Definition	It is the amount of energy supply to one coulomb of charge.	The amount of energy used by one coulomb of charge in moving from one point to another.
Unit	Volt	Volt
Symbol	ε	V
Source	Dynamo or Battery	Battery
Resistance	Independent from the resistance of the circuit	Proportional to the resistance of the circuit.
Current	It transmits current throughout the circuit.	It transmits current between any two points.
Magnitude	Greater than the potential difference between any two points	Always less than the maximum value of emf when the battery is fully charged.
Variation	It remains constant	Does not remain constant.
Relation	Cause	Effect
No current	Not Zero	Zero
Voltage	It is the maximum voltage that the battery can transfer	It is less than the maximum voltage that cell can deliver.
Field	Causes in magnetic, gravitational and electric field.	Induces only in electric field
Energy	Gain energy	Loss energy
Measuring Instrument	EMF Meter	Voltmeter

Definition of Potential Differences

The potential difference is defined as the amount of energy used by one coulomb of charge in moving from one point to the other. It is measured in volts and represented by the symbol  V. The potential difference is measured by the Voltmeter.

The potential difference between the two point charges is expressed by the formula shown below.

Example – Consider a circuit shown in the figure below.

A 12 volt supply applies across the resistance of the circuit. The potential difference between any two points, says A and B, is the energy used by one coulomb of charge in moving from one point (A) to the other (B). Thus, the potential difference between point A and B  is 7 volts.

Definition of Electromotive force

The electromotive force is the total voltage induce by the source. In other words, it is the amount of energy supplied by the source to each coulomb of charge. It is measured in volts and represented by the symbol ε (epsilon).

The emf is the maximum voltage that can be attained by the circuit. Naturally, it is generated when the fluctuation occurs in the magnetic field. The emf is expressed by the formula shown below

The electromotive force is the type of energy which forces a unit positive charge to move from the positive to the negative terminal of the source. It separates the two charges from each other.

Example – Consider a circuit shown in the figure below.

A battery has an EMF of 12V ; it means that the battery supplies 12 joules of energy to each coulomb of charge. The charge is travel from the positive terminal to negative terminal through an external circuit; it gives a whole of the energy originally supplied by the battery.

Point to Remember

At first sight, the name emf implies that it is a force that causes the electrons (charged particles, i.e., current) to flow through the circuit. In fact, it is not a force, but it is energy supplied by some active source such as a battery to one coulomb of charge.