Edexcel International A Level Physics

Revision Notes

2.46 Electromotive Force

Test Yourself

Electromotive Force

  • When charge passes through a power supply such as a battery, it gains electrical energy
  • The electromotive force (e.m.f.) is defined as:

The amount of chemical energy converted to electrical energy per unit charge when charge passes through a power supply

  • e.m.f. is measured in Volts (V)


emf definition, downloadable AS & A Level Physics revision notes

Definition of e.m.f. with regards to energy transfer

  • This can also be written as:

Emf energy equation


  • E.m.f. is:
    • represented by the symbol ε (greek letter epsilon)
    • not actually a force, but a measure of energy transferred per coulomb of charge
    • is measured in volts (V), which is J C−1 in S.I. units

  • e.m.f. is also the potential difference across the cell when no current is flowing
  • e.m.f. can be measured by connecting a high-resistance voltmeter around the terminals of the cell in an open circuit

 Measuring emf, downloadable AS & A Level Physics revision notes

e.m.f. is measured using a voltmeter connected in parallel with the cell


You've read 0 of your 0 free revision notes

Get unlimited access

to absolutely everything:

  • Downloadable PDFs
  • Unlimited Revision Notes
  • Topic Questions
  • Past Papers
  • Model Answers
  • Videos (Maths and Science)

Join the 80,663 Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?


Author: Joanna

Joanna obtained her undergraduate degree in Natural Sciences from Cambridge University and completed her MSc in Education at Loughborough University. After a decade of teaching and leading the physics department in a high-performing academic school, Joanna now mentors new teachers and is currently studying part-time for her PhD at Leicester University. Her passions are helping students and learning about cool physics, so creating brilliant resources to help with exam preparation is her dream job!