Circuit Symbols (Cambridge (CIE) A Level Physics)

Circuit symbols

• The diagrams below show the various circuit symbols that could be used in circuit diagrams. You will be expected to recognise and draw all of these

• The most common symbols are as follows:

Circuit symbols

Common circuit symbols

• The function of the most common components are:

  • Switch: Turn the circuit on (closed), or off (open)

  • Fixed resistor: A resistor limits the flow of current. A fixed resistor has a resistance it cannot change

  • Variable resistor: A resistor with a slider that can be used to change its resistance. Used often in dimmer switches and volume controls

  • Thermistor: The resistance of a thermistor depends on its temperature. As its temperature increases, its resistance decreases and vice versa

  • Light-dependent resistor (LDR): The resistance of an LDR depends on the light intensity. As the light intensity increases, its resistance decreases and vice versa

  • Diode: A diode allows current to flow in one direction only. They are used to convert AC to DC 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 component

  • Voltmeter: Use to measure the potential difference of an electrical component. Connected in parallel with component

• The more uncommon, yet relevant symbols, are as follows:

Uncommon circuit symbols

Other circuit symbols

Interpreting circuit diagrams

• Being able to draw and interpret circuit diagrams using circuit symbols is an essential skill in Electronics