Potential Difference and EMF
Potential difference is the energy transferred per unit charge between two points, measured in volts.
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Potential difference is the energy transferred per unit charge between two points, measured in volts.
- Measured with a voltmeter in parallel
- A cell provides an EMF
- Volts are joules per coulomb
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Potential Difference and EMF?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Potential Difference and EMF. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain Potential Difference and EMF in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Potential Difference and EMF explains how the physical world behaves, from sport and transport to electricity and medicine.
Potential Difference and EMF in detail
Potential difference (p.d.), or voltage, is the energy transferred per unit charge between two points: V = E/Q, measured in volts (V), where 1 V = 1 J/C. It is measured with a voltmeter connected in parallel across a component.
The electromotive force (e.m.f.) of a cell or battery is the energy it supplies to each coulomb of charge around the whole circuit. The e.m.f. is greater than the terminal p.d. when current flows, because of the internal resistance of the cell. In a series circuit, the p.d.s across the components add up to the supply voltage.
How the interactive helps you understand Potential Difference and EMF
Watch the circuit in the interactive. Use any sliders or buttons it offers to change the values and see how the circuit responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Potential Difference and EMF.
Real-life uses and examples
- Answer “explain” questions by linking Potential Difference and EMF to a clear cause and effect.
- Predict what a ball, car or circuit will do with Potential Difference and EMF before you do the calculation.
- Explain everyday devices, such as brakes, lifts or chargers, using Potential Difference and EMF.
Common mistakes to avoid
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Mixing up Potential Difference and EMF with a related quantity that has different units.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Potential Difference and EMF
What is Potential Difference and EMF?
Potential difference is the energy transferred per unit charge between two points, measured in volts.
What are the most important points about Potential Difference and EMF?
The main points are: Measured with a voltmeter in parallel; A cell provides an EMF; Volts are joules per coulomb.
Why is Potential Difference and EMF useful?
Understanding Potential Difference and EMF explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise Potential Difference and EMF?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Potential Difference and EMF?
Related topics in Physics include Electrical Power and Energy, Magnets and Magnetic Fields, Electromagnetic Induction.