Difference between EMF and Voltage

The most commonly asked question in the electrical subject is " What is the difference between EMF and voltage ". To understand the difference between EMF and voltage, let us first see about the terms EMF and voltage.

EMF

EMF means electromotive force. Electromotive force is defined as a voltage present at the terminal of the battery or source in the absence of electric current. It is the amount of energy supplied to each charge by the battery. It is measured in volts and it is denoted by the symbol ε or E.

Voltage

Voltage is the potential difference between the two points. Potential is defined as the amount of energy required by a unit charge to move from one point to another point. It is measured in volts and it is denoted by the symbol V.

Read this also: Difference between Current and Voltage

Difference between EMF and voltage

EMF is the voltage developed between the two terminals of the battery in the absence of electric current. Voltage is the potential difference between the two points. If there is a potential difference between the two points then, there will be a voltage.

EMF maintains the potential difference between the two points. External power source or battery also called EMF which maintains the potential difference between the two points.

Multimeter set to measure voltage | Image by DGerman at English Wikipedia, CC0, via Wikimedia Commons

EMF is open circuit voltage. Voltage is a closed circuit voltage. EMF is measured using a potentiometer. Voltage is measured using a voltmeter. EMF will be always constant but, the voltage can vary due to the drop at any electrical components.

An example of an EMF meter | Image by Rvcrewe at the English-language Wikipedia, CC BY-SA 3.0, via Wikimedia Commons

Finally, we can say that when there is a voltage there will be current which means the potential difference between the two points creates an electron flow path between them, whereas electron flow creates a current between these two points. When there is an EMF there will be a voltage which means EMF maintains the potential difference between the two points. EMF is a cause and voltage is an effect.