Series, parallel and bridge networks
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 1 worked example, 3 practice questions, 4 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Untangling a circuit
- Method
Read the transcript of the teaching part
Last time
Before we start: last time, in The potentiometer, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Untangling a circuit
A big network of resistors looks frightening. But every one is built from just two ideas: series, where the current is shared, and parallel, where the p.d. is shared. Work step by step, label what you know, and the circuit unwinds itself.
Method
First, redraw the circuit simply, and mark every known current and p.d. Second, replace each parallel block by its equivalent resistance, working from the inside out. Third, add the series resistances to find the total, then use V equals I R for the main current. Fourth, go back through each block: the p.d. is shared in parallel and the current is shared in series. Fifth, check: the currents at each junction add up, and the p.d.s around each loop add up.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Series and parallel.
The whole chapter: D.C. Circuits, D.C. Circuits.
Chapter 10.6: Resistor networks
- Series, parallel and bridge networks 8 min
Also for A Level Physics 9702
Which topics come up most in A Level Physics 9702 past papers, counted from every paper since 2004: Paper 1 topic frequency, Paper 2 topic frequency.