ElectricityTopic Summary
Knowledge Organiser: Series and Parallel Circuits
Part of Series & Parallel Circuits · GCSE GCSE Physics revision
This topic summary covers Knowledge Organiser: Series and Parallel Circuits within Series & Parallel Circuits for GCSE Physics. Revise Series & Parallel Circuits in Electricity for GCSE Physics with 20 exam-style questions and 30 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 16 of 16 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 16 of 16
Practice
20 questions
Recall
30 flashcards
Knowledge Organiser: Series and Parallel Circuits
Series Rules
- Current: same everywhere
- Voltage: adds up to supply
- Resistance: R = R₁ + R₂ + R₃
- One breaks: all stop
Parallel Rules
- Voltage: same on each branch
- Current: I = I₁ + I₂ + I₃
- Resistance: 1/R = 1/R₁ + 1/R₂
- R always less than smallest branch R
Key Equations
- Series R: R = R₁ + R₂
- Parallel R: 1/R = 1/R₁ + 1/R₂
- 2 resistors parallel: R = (R₁×R₂)/(R₁+R₂)
Exam Tips
- Parallel R always less than smallest
- Solve parallel group first, then add series
- Houses = parallel (independence)
- Check: parallel answer must be small
Common Mistakes
- Adding parallel resistances directly: For parallel resistors, use 1/R_total = 1/R₁ + 1/R₂ — adding them directly gives the wrong (too large) answer
- Thinking parallel resistance is larger: Adding resistors in parallel always decreases total resistance — the total is always less than the smallest individual resistor
- Forgetting current splits in parallel: In a parallel circuit, current splits between branches — the branch with lower resistance carries more current
- Applying series voltage rule to parallel: In parallel, all branches have the same voltage; in series, voltage divides — don't mix these up
- Removing a component affects series but not parallel: In series, removing one component breaks the whole circuit; in parallel, other branches continue to work