Electrical circuit symbols

Symbols

The following symbols show the different components that can be found in an electrical circuit.

Components

Some of the more common components are:

Switch

A switch used to turn a circuit on (closed) and off (open).

Lamp

An electrical current heats the filament in a bulb so that it gives out light.

Fixed resistor

A resistor restricts or limits the flow of electrical current. A fixed resistor has a resistance that does not change.

Variable resistor

Moving the position of the slider on this resistor, changes the resistance. A variable resistor is used in some dimmer switches and volume controls.

Thermistor

The resistance of a thermistor depends on its temperature. At low temperatures, the thermistor has a high resistance. As the temperature increases, the resistance decreases. A thermistor can be used in thermostats or heat activated fire alarms.

Light-dependent resistor (LDR)

The resistance of a LDR depends on light intensity. At low light levels, the LDR has a high resistance. As the light intensity increases, the resistance decreases. A LDR can be used as a sensor in cameras or automatic lights that come on when it gets dark.

Semiconductor diode

A semiconductor diode allows current to flow in one direction only. Current will not flow in the other direction. Diodes are used to convert an alternating current into a direct current.