This topic summary covers Knowledge Organiser: Potential Difference 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 14 of 14 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Potential Difference
Key Terms
- Potential difference: Energy per unit charge (V)
- Volt: 1 J per coulomb
- EMF: Energy given by supply per coulomb
- Voltmeter: Measures p.d.; in parallel
Key Facts
- Series: voltages add up to supply
- Parallel: same voltage across each branch
- Voltmeter in parallel; ammeter in series
- 1 V = 1 J/C
Key Equations
- V = E / Q
- E = V × Q
- Q = E / V
Exam Tips
- Voltmeter = parallel (always)
- Series: missing V = supply − others
- Parallel: all branches = supply voltage
- State units: V, J, C
Common Mistakes
- Placing voltmeter in series: Voltmeters must always be connected in parallel across a component — never in series
- Confusing voltage and energy: Voltage (V) is energy per unit charge (J/C) — it is not the same as energy; a large voltage does not mean a large total energy
- Forgetting voltage splits in series: In a series circuit, voltages across components add up to the supply voltage — always check they sum correctly
- Saying voltage is "used up": Voltage is a measure of energy transferred per coulomb — the charge carries less energy after passing through a component, but charge itself is conserved
- Mixing up EMF and terminal voltage: EMF is the voltage supplied by the source; terminal voltage is slightly less due to internal resistance of the battery
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.
Quick recall flashcards
What is 1 Volt?
1 Joule per Coulomb (1 V = 1 J/C)
P.d. equation?
V = E/Q where V = voltage (V), E = energy (J), Q = charge (C). Also V = IR.