This higher tier covers Higher Tier Only: EMF and Internal Resistance within Potential Difference for GCSE Physics. Revise Potential Difference in Electricity for GCSE Physics with 14 exam-style questions and 30 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 11 of 14 in this topic. This section is most useful once the core foundation idea is secure, because it adds the detail that pushes answers higher.
🎓 Higher Tier Only: EMF and Internal Resistance
A real battery has internal resistance (r) — the resistance of the battery itself. This means the voltage you measure at the battery's terminals (terminal p.d.) is slightly less than the EMF.
The "lost volts" (Ir) is the voltage "used up" inside the battery itself. A battery with high internal resistance will show a significantly lower terminal voltage when supplying large currents — this is why old batteries struggle to start cars on cold mornings.
Practice questions for Potential Difference
Which of the following is the correct definition of potential difference?
Explain what is meant by a potential difference of 6 V across a component.