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Standard circuit symbols

Syllabus
2024
Topic
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Level
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Learning objectives

—Recognise and use standard circuit symbolsRecognise and use the examination circuit symbols for conductors crossing without a connection, a junction, open switch, cell, battery, DC and AC power supplies, transformer, ammeter, voltmeter, fixed and variable resistors, heater, thermistor, light-dependent resistor (LDR), diode, light-emitting diode (LED), lamp, loudspeaker, microphone, electric bell, earth or ground, motor, generator, and fuse or circuit breaker. Other internationally agreed symbols may be accepted in answers.

Read and use the full circuit-symbol language

A circuit symbol identifies a component or electrical connection without showing its physical appearance. Recognise the decisive marks in the examination set, then use the same symbols consistently when drawing a circuit.

Family Examination symbols and decisive recognition cues
Connections and control Crossing conductors have no dot; a junction has a filled dot; an open switch has a visible gap and raised contact arm.
Sources and transfer A cell has one long and one short parallel line; a battery repeats cell pairs; a DC supply is marked ++ and −-; an AC supply is marked ∼\sim; a transformer has two facing coils.
Measurement and resistance Ammeter and voltmeter are circles containing A and V. A fixed resistor is a rectangle; a variable resistor adds a diagonal arrow; a heater uses a segmented resistor; a thermistor adds a diagonal temperature mark; an LDR has arrows pointing towards the resistor.
One-way and light devices A diode points towards its blocking bar; an LED is the diode symbol with arrows pointing outwards; a lamp is a circle containing a cross.
Sound and motion A loudspeaker has a cone profile; a microphone has a diaphragm profile; an electric bell has a bell dome; motor and generator are circles containing M and G.
Reference and protection Earth or ground ends in three progressively shorter horizontal bars; a fuse or circuit breaker is a narrow rectangle with the conductor line through it.

Join component terminals with straight conductor lines and show a filled dot only where branches connect. Put an ammeter in series with the branch whose current is required. Put a voltmeter in parallel across the component whose potential difference is required. Preserve the polarity of cells and DC supplies, and orient diodes and LEDs so their permitted current direction matches the intended circuit.

A drawing that resembles the real component is not a circuit symbol. Do not confuse a crossing with a junction, inward LDR arrows with outward LED arrows, or meter position with meter identity. Pearson uses the Appendix 8 forms in examination papers, although another internationally agreed form may be accepted in a student answer.