Back Electronic/Electrical Symbols

Electronic/Electrical Symbols

Name Symbol Notes
Resistor Resistor Resists current flow
Resistor, tapped Tapped resistor A fixed resistor having one or more additional terminals along its length, generally for voltage-divider applications
Resistor, variable (potentiometer) Potentiometer Three terminals; usually used to control voltage
Resistor, variable (rheostat) rheostat Two terminals; usually used to control current
Photoresistor Photoresistor Converts light to resistance
Thermistor thermistor Thermal resistor; resistance varies significantly with temperature
Capacitor, non-polar Nonpolar capacitor Stores electric charge; acts as short circuit with AC and open circuit with DC
Capacitor, polar Polar capacitor Only operates properly when connected to proper polarity (one lead is positive, the other negative)
Capacitor, variable Variable capacitor Capacitance may be varied mechanically or electronically
Inductor Inductor Generates magnetic field
Inductor, iron core Iron core inductor Uses a ferromagnetic core to increase inductance
Inductor, variable Variable inductor Provides varying output voltage
Inductor, variac Variac inductor Variable autotransformer providing a continuously adjustable output voltage
Inductor, tapped Tapped inductor Taps allow for different voltage outputs
Diode Diode Allows current flow in one direction only (in direction of arrow)
Light emitting diode (LED) LED Emits light when current flows through
Photodiode Photodiode Allows current flow when exposed to light
Tunnel diode Tunnel diode Has a negative resistance at very low voltage
Varactor Varactor Used as a voltage-controlled capacitor
Zener diode Zener diode Allows current flow in one direction, but also can flow in the reverse direction when above breakdown voltage
Transistor, NPN NPN transistor Allows current flow when the collector voltage is larger than the emitter voltage
Transistor, PNP PNP transistor Allows current flow when the emitter voltage is larger than the collector voltage
Phototransistor Phototransistor Allows current flow when exposed to light
Pushbutton, normally open Pushbutton, normally open Allows current to flow only when pressed
Pushbutton, normally closed Pushbutton, normally closed Open (off) only when pressed
Single-pole, single-throw (SPST), normally open SPST, normally open Simple on-off switch
Single-pole, single-throw (SPST), normally closed SPST, normally closed Open (off) only when switched
Single-pole, double-throw (SPDT) SPDT A changeover switch; has two "on" positions and one "off" position
Double-pole, single-throw (DPST) DPST A dual on-off switch; simultaneously opens or closes two separate circuits or both sides of the same circuit
Double-pole, double-throw (DPDT) DPDT Consists of two separate switches that operate at the same time, with one normally open and one normally closed
Electron Tubes
Diode Diode Two electrodes--cathode (C) and plate (P) (the plate is also known as the anode (A)); the heater (H) is used to stimulate electron flow
Glow tube Glow tube Diode used for voltage regulation
Phototube Phototube Diode that is sensitive to light; current flow is dependent on intensity and frequency of incoming photons
Triode Triode Three electrodes--cathode (C), plate (P), and grid (G)
Tetrode Tetrode Four electrodes--cathode (C), plate (P), grid (G), and screen (S)
Beam tetrode Beam tetrode Beam-forming electrodes allow more power output than a similar pentode
Pentode Pentode Five electrodes--cathode (C), plate (P), grid (G), screen (S), and suppressor (Sup)
AC power supply AC power supply Provides AC power
Antenna Antenna Transmits/receives radio waves
Antenna, dipole Dipole antenna Two-wire antenna
Amplifier Amplifier Increases input signal
Battery Battery Provides DC power
Cell Cell Batteries contain one or more cells
DC power supply DC power supply Provides DC power
Fuse Fuse Opens when subjected to current above stated threshold
Generator Generator Converts mechanical energy into electrical energy
Ground, earth Earth ground Provides electrical shock protection
Ground, chassis Chassis ground Connected to circuit chassis
Ground, signal (common) Signal ground Reference point for all signals in a circuit; commonly, the same as the circuit ground
Headphones Headphones Converts electrical signals to sound waves
Lamp Lamp Used for indicating or lighting
Loudspeaker Loudspeaker Converts electrical signals to sound waves
Meter Meter *A - ammeter
DB - decibel meter
F - frequency meter
G - galvanometer
MA - milliammeter
Ω - ohmmeter
V - voltmeter
W - wattmeter
Microphone Microphone Converts sound waves to electrical signals
Motor Motor Converts electrical energy into mechanical energy
Piezoelectric crystal Piezoelectric crystal Converts electrical energy to sound waves
Relay Relay Opens and closes connections with an electromagnet
Transformer Transformer Changes AC voltage from high to low (step-down) or low to high (step-up)
Wire Wire Electrical current conductor
Wires, joined Joined wires Connected crossing wires
Wires, not joined Wires not joined Unconnected crossing wires