Electronics and Electrical Symbols

Electrical Wire

Connected Wires

Not Connect Wires

DC Voltage Source

Voltage, V

defined as energy per unit of charge.

Current, A

is the rate of flow of charge.

Resistance, Ω

is the opposition to current.

AC Voltage Source

Current Source

can provide a constant current in any load. Just as in the case of a voltage source, the ideal current source does not exist but can be approximated in practice.

Current Source

Resistors

Components that are specifically designed to have a certain amount of resistance. The principal applications of resistors are to limit current, divide voltage, and, in certain cases, generate heat.

Resistor

Variable Resistors

are designed so that their resistance values can be changed easily.

Variable Resistance Sensors

Physical quantity alters the electrical resistance

Potentiometer

Used to divide voltage

Potentiometer

Rheostat

Used to control current

Rheostat

Thermistor

change resistance as a function of temperature

Thermistor

Photoconductive Cell

change resistance as a function of light

Photoconductive Cell

Strain Gauges

change resistance when a force is applied to them

Strain Gauges

Switches

Commonly used for controlling the opening or closing of circuits

SPST

SPDT

DPST

DPDT

NOPB

NCPB

Single-pole rotary (6-position)

Single Pole Single Throw (SPST)

switch controls a single circuit

Single Pole Double Throw (SPDT)

switch has a single pole and two different switch output options.

Double-pole–single-throw (DPST)

switch permits simultaneous opening or closing of two sets of contacts.

Double-pole–double-throw (DPDT)

switch provides connection from one set of contacts to either of two other sets.

normally open push-button switch (NOPB)

the connection is made between two contacts when the button is depressed, and the connection is broken when the button is released

normally closed push-button switch (NCPB)

the connection between the two contacts is broken when the button is depressed.

rotary switch

a knob is turned to make a connection between one contact and any one of several others

Protective Devices

FUSES and CIRCUIT BREAKERS are placed in the current path and are used to deliberately create an open circuit when the current exceeds a specified number of amperes due to a malfunction or other abnormal condition in a circuit.

Fuse symbol

Circuit breaker symbol

Ground

The reference point in an electric circuit.

Reference Ground

Chassis Ground

Alternate reference symbol

Capacitor

A passive electrical component that stores electrical charge and has the property of capacitance.

is an electrical device constructed of two parallel conductive plates separated by an insulating material called the dielectric.

Basic Capacitor

Electrolytic Capacitor

Variable Capacitor

Inductor

An inductor is a passive electrical component, formed by a coil of wire, that exhibits the property of inductance.

When a length of wire is formed into a coil, it becomes an inductor.

Fixed (Inductor)

Variable (Inductor)

Air core

Iron core

Ferrite core

Diode

A diode conducts current when it is forward-biased when the bias voltage exceeds the barrier potential. A diode prevents current when it is reverse biased at less than the breakdown voltage.

Diode

Zener Diode

is designed for operation in the reverse breakdown region.

Zener Diode

Varactor Diode

A varactor is basically a reverse-biased pn junction diode that utilizes the inherent capacitance of the depletion region.

Varactor Diode

LED

is a semiconductor device that emits light when an electric current flows through it.

LED

Photodiode

A photodiode is a semiconductor device that convers photons (light) into electrical current.

Photodiode

Tunnel Diode

is a very heavily doped p-n junction diode. In a Tunnel diode electric current decreases as the applied voltage increases, and at high voltage, it works as an ordinary p-n junction diode.

Tunnel Diode

Schottky Diode

is formed by the junction of a semiconductor with a metal, also known as hot-carrier diode.

Schottky Diode

Transistors

is a semiconductor device that controls current between two terminals based on the current or voltage at a third terminal and is used for the amplification or switching of electrical signals.

Bipolar Junction Transistor (BJT)

(BJT) npn

(BJT) pnp

(JFET) n channel

(JFET) p channel

Transistors

is a semiconductor device that controls current between two terminals based on the current or voltage at a third terminal and is used for the amplification or switching of electrical signals.

MOSFET

Metal Oxide Semiconductor Field Effect Transistor

Enhancement MOSFET (E-MOSFET)

(E-MOSFET) n channel

(E-MOSFET) p channel

Depletion MOSFET (D-MOSFET)

(D-MOSFET) n channel

(D-MOSFET) p channel

Thysristors

The device acts as a switch and remains off until the forward voltage reaches a certain value; then it turns on and conducts. Conduction continues until the current is reduced below a specified value.

Shockley Diode

Silicon-Controlled Rectifier (SCR)

Light-Activated Silicon-Controlled Rectifier (LASCR)

Silicon-Controlled Switch (SCS)

Unijunction Transistor (UJT)

DIAC

TRIAC

Programmable Unijunction Transistor (PUT)

Voltmeter

Ammeter

Ohmmeter