Cambridge IGCSE Physics Notes 4.3: Electric Circuits
Cambridge IGCSE Physics circuit notes on symbols, series and parallel rules, combined resistance, potential dividers, thermistors, LDRs, and relays.
Q: What does Cambridge IGCSE Physics Notes 4.3: Electric Circuits cover?
A: It follows official Cambridge Physics section 4.3 for syllabuses 0625 and 0972, with Core ideas separated from Supplement depth.
Circuit behaviour follows conservation of charge and energy: current is shared at junctions, while potential differences across components account for energy transfers.
The ideas that organise this section
- Current is the same throughout a series path and divides at parallel junctions.
- Series potential differences add to the supply, while parallel branches share the same potential difference.
- Component resistance can respond to temperature, light, or applied voltage.
Core route
Core candidates should be ready to describe, calculate, interpret, and apply the following:
- Recognise and draw standard circuit symbols.
- Apply series and parallel current and voltage rules.
- Describe uses of diodes, LEDs, thermistors, LDRs, relays, and variable resistors.
Supplement route
Extended candidates study all Core content and add the following depth:
- Calculate combined resistance for series and parallel networks within syllabus scope.
- Analyse potential-divider circuits and sensor outputs.
- Explain component action from current-voltage characteristics.
Formula route
- Relationship: series resistance = first resistance + second resistance + ....
- Relationship: parallel conductance = sum of branch conductances.
Write the relationship before substituting. Convert units first, keep extra figures during working, and round only the final answer to sensible precision.
Build a connected model
In Electric Circuits, a strong answer connects the named quantity or model to observable evidence. Begin by defining the physical quantity in words or with its relationship. Identify which values are scalars and which require a direction. Represent the situation with a labelled diagram, graph, field pattern, ray or circuit when that makes the relationship visible. The representation is part of the reasoning: its labels, arrows and scale should agree with the written explanation.
For a calculation, write the governing relationship before substitution, convert prefixes and time units, keep unrounded values during working and attach the correct final unit. For a qualitative question, use a cause-link-consequence chain. Name what changes, state the physical mechanism that links the change to the system, and then give the measurable result. If two cases are compared, hold unrelated variables constant and use the same physical principle for both.
