The following symbols show the different components that can be found in an electrical circuit.
Some of the common components are:
A switch is used to turn a circuit on (closed) and off (open).
Moving the position of the slider on this resistor, changes the resistance. A variable resistor is used in some dimmer switches and volume controls.
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.
The resistance of an LDR 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 automatic lights that come on when it gets dark.