Circuit Symbols (Oxford AQA IGCSE Combined Science Double Award)
Revision Note
Written by: Ann Howell
Reviewed by: Caroline Carroll
Circuit Symbols
All students in the GCSE examination will be expected to draw and interpret circuit diagrams using the following symbols:
Common circuit symbols
The functions of the most common components are:
Cell / battery: Provides the circuit with a source of potential difference. A battery is two or more cells
Switch: Turn the circuit on (closed), or off (open)
Fixed resistor: A resistor limits the flow of current. A fixed resistor has a resistance that cannot change
Variable resistor: A resistor with a slider that can be used to change its resistance. These are often used in dimmer switches and volume controls
Diode: A diode allows current to flow in one direction only. They are used to convert A.C. to D.C. current
Light-emitting diode (LED): This is equivalent to a diode and emits light when a current passes through it. These are used for aviation lighting and displays (TVs, road signs)
Ammeter: Used to measure the current in a circuit. Connected in series with other components
Voltmeter: Use to measure the potential difference of an electrical component. Connected in parallel with the relevant component
Sensors
Thermistor: The resistance of a thermistor depends on its temperature
As its temperature increases, its resistance decreases and vice versa
Thermistors are used in the thermostats of heating devices such as radiators and kettles
Thermostats regulate the temperature of an area or substance (e.g. ensuring a room stays at 20 °C)
Light-dependent resistor (LDR): The resistance of an LDR depends on the light intensity of the surroundings
As the light intensity increases, its resistance decreases and vice versa
LDRs are used on street lamps, so they turn on automatically when it gets dark and the light intensity gets lower
Examiner Tips and Tricks
You may be asked to comment on the accuracy of an electrical circuit or draw a suitable one. Look out for the following features:
An energy source
A source of potential difference
A closed path or a complete circuit
Electrons need to flow in a complete loop for a current to flow.
A circuit can be opened and closed using a switch
Electrical components must be drawn with the correct circuit symbol and include:
Sensors that respond to the environment such as an LDR or thermistor
Measuring devices e.g. an ammeter or voltmeter
Components that transferring energy to other stores, such as an LED or lamp
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