Circuit symbols,
drawn both ways.
On a schematic, each symbol stands for a circuit element: one of the components that make up the circuit, such as a power supply, a switch or a capacitor. The connections between elements are the circuit's nodes.Source 1Source 2 Here each symbol is drawn in its US and international (IEC) form, with its terminals named. For parts that change state, pick a setting and see which path conducts while the printed symbol stays put.
Read, practise, print
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Read a schematic
Tap a wire and its whole node lights up. Four reading rules, six practice circuits, and an answer for every question.
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Check your reading
Short question sets with a written reason for every answer. Nothing is scored or saved.
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Take it to paper
A4 and US Letter drawing sheets: a blank naming exercise, its answer key and a labelled reference, in either style.
Try it: energise the relay
Relay sheetCOM–NC conducts. Under the single-stable relay model, the coil is de-energised and settled: COM–NC is closed and COM–NO is open. This is the drawn resting state.
COM–NO conducts. Under the single-stable relay model, the coil is energised and settled: COM–NO is closed and COM–NC is open. The printed contact stays at rest; only the highlight shows the present position.
Symbol sheets
All drawings on one chartOne part, two drawings
What changes, symbol by symbol22 of the 41 symbols on the chart change between the two styles. The US and IEC switch at the top of every page picks the style the sheets show; here both stay in view.
US style names the American drawing convention used here, including the resistor zigzag. IEEE 315-1975 (ANSI Y32.2) is a historical reference; IEEE lists it as inactive-reserved, with inactivation dated 7 November 2019.Source 3Source 4
IEC style names the international drawing convention used here, including the rectangular resistor. IEC 60617 is the reference database for diagram symbols; these teaching drawings are explained using the open sources cited beside them.Source 4Source 5
What a symbol does not tell you
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Whether current is flowing
The diode's triangle points the way conventional current flows through it during forward conduction, from anode to cathode. The triangle does not say whether the diode is conducting: that depends on the anode's potential relative to the cathode.Source 6Source 7Source 8
Set the potentials on the diode sheet -
Where the leads are
A schematic symbol shows how terminals connect, not where they are on a real part. Terminal letters such as E, B and C or A and K do not give lead order or package layout; the part's own documentation does.Source 1Source 9Source 10
B, C and E on the transistor sheet -
Where the part sits
A schematic describes electrical connections only, not where parts sit. Parts can be moved or redrawn anywhere on the page without changing the circuit, as long as every connection is kept.Source 1
Follow the connections on the reading page
Often confused
Drawings that are easy to mix up, each answered on its sheet with the one mark that tells them apart.
Sources
10 sources, numbered as cited
- Electrical Schematics, §§1.3.1–1.3.5 — nodes, crossings, references and congruent drawings
- Lessons In Electric Circuits, Vol. V — §9, Circuit Schematic Symbols (pp. 130–139)
- IEEE 315-1975 — historical standard status
- ModEL — Components and Symbols, §§3.4–3.6 (NEMA and IEC symbol families, pp. 11–13)
- IEC 60617:2026 DB — Graphical symbols for diagrams
- ModEL — PN Junctions and Diodes, §§2.3–2.7 (bias and diode variants)
- ModEL — Components and Symbols, §3.16 (diodes, p. 29)
- Diodes — terminal polarity, ideal and offset models (pp. 1–2, 7–10)
- ModEL — Semiconductor Logic Gates, §2.1 (schematic versus package pinout, p. 8)
- ModEL — Electromechanical Relays, §§3.2–3.3 and §5.1 (normal and present contact status)