LEDs (Oxford AQA IGCSE Combined Science Double Award)
Revision Note
Written by: Ann Howell
Reviewed by: Caroline Carroll
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
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 Tips and Tricks
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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