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Potential Difference - GCSE Physics Definition

Reviewed by: Ann Howell

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What is Potential Difference?

In GCSE Physics potential difference is the work done by a unit of charge as it passes through a circuit component. It is also known as potential difference and is measured in volts. 

The potential difference between two points in a circuit is a measure of how much energy is transferred between these two points. Some exam boards are specific about the terminology required for their definition, so use the Save My Exams specific course revision notes for AQA GCSE, Edexcel GCSE, OCR Gateway GCSE and WJEC GCSE. to ensure you learn the correct one for your exam.

An electrical circuit featuring a power supply with a fixed resistor and a bulb. A voltmeter is connected in parallel to the resistor.
A voltmeter is connected in parallel to an electrical component to measure the amount of energy transferred to it. Here the voltmeter is measuring the amount of potential difference across the resistor.

As charge flows around a circuit energy is transferred to or from the charge. The potential difference across a component is therefore a measure of the amount of energy transferred by this charge as it flows through a component in the circuit. This means that potential difference can be calculated using the equation

potential space difference space equals space fraction numerator energy space transfered over denominator charge space moved end fraction

A battery or cell has a positive terminal at one end and a negative terminal at the other. An EMF or electromotive force is generated between the terminals. The e.m.f  is the total amount of potential difference present in the power source of a circuit. This is generated by a cell, batteries which are multiple cells or an electrical generator. The sum of the total amount of potential difference used by each component in the circuit is equal to the e.m.f.

A power supply has an e.m.f of 12 V and is connected to a fixed resistor with a potential difference of 7 V and a bulb with a p.d. of 5 V
The e.m.f in the power supply is the sum of the potential difference across each component in the circuit

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Ann Howell

Reviewer: Ann Howell

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Ann obtained her Maths and Physics degree from the University of Bath before completing her PGCE in Science and Maths teaching. She spent ten years teaching Maths and Physics to wonderful students from all around the world whilst living in China, Ethiopia and Nepal. Now based in beautiful Devon she is thrilled to be creating awesome Physics resources to make Physics more accessible and understandable for all students, no matter their schooling or background.

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