Circuit diagrams use STANDARD SYMBOLS so that any engineer or scientist worldwide can read and build the same circuit — regardless of language.
A circuit diagram shows how components are connected using straight lines (wires) and standardised symbols. It is a schematic, not a picture of the physical layout.
Rules for drawing circuit diagrams:
Use a RULER — all lines must be straight.
Components are placed on the lines, not at corners.
Circuit should be drawn as a CLOSED LOOP.
Wires are shown as straight horizontal and vertical lines.
Essential Component Symbols
You must be able to draw and recognise all of these — the AQA list:
POWER SUPPLIES:
Cell — one long line (positive) + one short line (negative)
Battery — two cells joined by a dashed line (two or more cells in series)
CONTROL:
Switch (open) — a lever angled away from its second contact
Switch (closed) — the lever touching both contacts
OUTPUT COMPONENTS:
Lamp — circle with a cross inside
LED — diode symbol with two arrows pointing out
MEASUREMENT:
Ammeter — circle with A (connected in SERIES)
Voltmeter — circle with V (connected in PARALLEL)
RESISTANCE:
Resistor — rectangle
Variable resistor — rectangle with a diagonal arrow through it
Thermistor — rectangle with a diagonal line through it, ending in a short horizontal tail
LDR (light-dependent resistor) — small rectangle inside a circle, with two arrows pointing in
OTHER:
Diode — triangle pointing to a bar (current flows in the direction of the triangle)
Fuse — rectangle with a line running through it along its length
Reading and Drawing Circuit Diagrams
To INTERPRET a circuit diagram:
1. Trace the path from the positive terminal of the battery.
2. Identify all components along each branch.
3. Note which components are in series (same path) and which are in parallel (different branches).
To DRAW a circuit diagram:
1. Sketch the battery and switch first.
2. Add components in the correct positions.
3. Connect everything with straight ruled lines.
4. Add meters: ammeter in series with the component; voltmeter in parallel across it.
COMMON EXAM TASK:
Given a description of a circuit, draw it accurately with all components in the correct positions and symbols drawn correctly.
⚠️ Common Mistake
Ammeters are connected IN SERIES — they must be in the same loop as the component. Voltmeters are connected IN PARALLEL — they bridge across the component. Swapping these will give wrong readings (and could damage the meter). Always draw with a ruler — freehand diagrams lose marks.
📌 Key Note
Standard symbols allow universal reading of circuits. The AQA symbols: switch (open and closed), cell, battery, diode, resistor, variable resistor, LED, lamp, fuse, voltmeter, ammeter, thermistor, LDR. Ammeter in series. Voltmeter in parallel.
🎯 Matching Activity — Component to Job
Match each component to what it does or how it is connected. — drag the symbols on the right to match the component names on the left.
Ammeter
Drop here
Voltmeter
Drop here
LDR
Drop here
Thermistor
Drop here
Diode
Drop here
Resistance decreases as light intensity increases
Connected in series — measures current
Connected in parallel — measures potential difference
Lets current flow in one direction only
Resistance decreases as temperature increases
🧪 Required Practical
🔬 RP15 (Physics) — Use circuit diagrams to set up and investigate circuits. RP16 — Construct circuits to investigate I–V characteristics.
Know the method, variables, equipment and how to analyse results.
🎯 Test Yourself
Question 1 of 2
1. How should an ammeter be connected to measure the current through a lamp?
2. A lamp and a resistor are connected in series with a cell. How should a voltmeter be connected to measure the potential difference across the lamp?
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