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LEDs (Oxford AQA IGCSE Combined Science Double Award)

Revision Note

Ann Howell
Oxford AQA Combined Science Double Award: PhysicsOxford AQA Physics

LEDs

  • Light-emitting diodes (LEDs) are a type of diode

  • They illuminate when placed in the correct direction (forward bias) when a current flows in a circuit

  • Since the LED has a visual response to current, it can be used to indicate the presence of a current in a circuit

LED circuit symbol

An LED circuit symbol has a triangle facing in the direction of current flow, a straight line perpendicular to the wire and two parallel arrows pointing away from the triangle.
LEDs indicate the presence of a current because they illuminate when current flows through them.

  • LEDs are being used increasingly for all lighting purposes because they are so efficient (they require a very low current)

    • They convert the most energy from the electrical store to the light energy store compared to any other type of bulb

Examiner Tip

Make sure you learn the differences between the symbols for an LDR and an LED

  • Two arrows pointing towards a symbol mean that it is light-dependent

  • Two arrows pointing away mean that it is light-emitting

Symbols are sometimes drawn with circles around them (e.g. the LDR). These circles are often optional (although not for meters and bulbs).

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    Ann Howell

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