Standard symbols
Electric circuit 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 is used to turn a circuit on (closed) and off (open).
When the switch is open, there is a break in the circuit and current stops flowing.
Lamp
An An electric current is a flow of charged particles in one direction. In solids, an electric current is the flow of free electrons in one direction. heats the filament in a bulb so that glows white hot and 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
Adjusting this resistor changes its resistance.
A variable resistor is used in some dimmer switches and volume controls.
Thermistor
The resistance of a thermistor depends on its temperature.
One type of thermistor is called an NTC thermistor (negative temperature coefficient).
At low temperatures, the NTC 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 is a class of material between a good conductor and an insulator.
Examples of semiconducting materials include silicon and germanium.
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.
Cell
A chemical reaction occurs inside a cell with chemical energy being converted to electrical energy.
A cell has a positive terminal and a negative terminal.