← Schematics & Diagrams

The Toolbox — Symbols

Electrical Symbols

Standard electrical schematic symbols for resistors, capacitors, inductors, semiconductors, switches, and power components.

ResistorFixed resistor. Opposes current flow. Value in ohms (Ω).
Variable Resistor (Potentiometer)Adjustable resistor with three terminals. Used for volume controls and voltage dividers.
Capacitor (Non-Polarized)Stores electrical energy in an electric field. Value in farads (F). No polarity — can be connected either way.
+
Capacitor (Polarized)Electrolytic capacitor with polarity — positive terminal marked with curved plate. Must be connected correctly.
InductorStores energy in a magnetic field. Value in henries (H). Used in filters, tuning circuits, and RF chokes.
DiodeAllows current to flow in one direction only. Anode (+) on left, cathode (−) on right (bar side).
Zener DiodeDiode designed to operate in reverse breakdown at a precise voltage. Used as voltage reference and protection.
LEDLight Emitting Diode. Emits light when forward biased. Arrows indicate light emission.
C E B
NPN TransistorBipolar junction transistor. Current flows from collector to emitter when base is forward biased. Arrow points out.
E C B
PNP TransistorBipolar junction transistor. Current flows from emitter to collector when base is pulled low. Arrow points in.
D S G
N-Channel MOSFETMetal-Oxide-Semiconductor Field-Effect Transistor. Voltage-controlled switch. Gate draws no DC current.
Switch (SPST)Single Pole Single Throw. Basic on/off switch. Open = no current flow, closed = current flows.
Ground (Earth)Reference point of zero volts. Earth ground — physically connected to earth via ground rod or building ground.
Chassis GroundConnected to the metal chassis or frame of equipment. Common in automotive and avionics wiring.
+ −
Battery / DC SupplyDC voltage source. Long line = positive terminal, short line = negative terminal.
Voltage Source (AC)AC voltage source — sinusoidal waveform. Used to represent mains power or signal generators.
FuseOvercurrent protection device. The element melts when current exceeds rated value, breaking the circuit.
TransformerTransfers electrical energy between circuits via electromagnetic induction. Steps voltage up or down.
− +
Op-AmpOperational Amplifier. High-gain differential amplifier. Inverting (−) and non-inverting (+) inputs.