Circuit symbols
Symbols
The following symbols show the different A device in an electric circuit, such as a switch or lamp. that can be found in an electrical circuit.
Some of the more common components are:
Switch
Lamp
A switch is used to turn a circuit on (closed switch) and off (open switch).
An electrical Moving electric charges, eg electrons moving through a metal wire. heats the A thin, high resistance wire that gets hot and glows when a current flows through it causing it to emit heat and light. Filaments are used in some types of bulb and electrical heaters. in a bulb so that it gives out light.
Fixed resistor
Variable resistor
A resistor limits the passage of electrical current. A Electrical component with a resistance that is fixed and cannot be changed. has a The opposition in an electrical component to the movement of electrical charge through it. Resistance is measured in ohms. that does not change.
The resistance of this resistor is changed by moving the position of a slider. A A resistor where the value of the resistance can be changed. is used in some dimmer switches and volume controls.
Thermistor
Light-dependent resistor (LDR)
The resistance of a An electrical device whose resistance decreases as its temperature increases. 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.
The resistance of a A Light Dependent Resistor is a type of resistor which is affected by changes in light levels. A cadmium sulphide layer causes a decrease in resistance in the light and increase in the dark. depends on light intensity. At low light levels, the LDR has a high resistance. As the light intensity increases, the resistance decreases. An LDR can be used as a sensor in cameras or in security lights that come on automatically when it gets dark.
Diode
A An electrical device that allows current to flow in one direction only. allows current to flow in one direction only. Diodes are used to convert an Also called ac. An electric current that regularly changes its direction and size. into a Direct current is the movement of charge through a conductor in one direction only..
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