• The short leg is the cathode.
  • The long leg is the anode.
  • Different colours are achieved by using different materials within the LED.

Ideal Conditions:

  • The ideal current for most LEDs is 20mA.
  • The ideal forward voltage for most LEDs is 2V.
  • It is possible to use Ohm’s law to find the best resistance for the protection resistor:
    • The below method assumes the input voltage is 9V:

V=I x R,

9V – 2V = 7V

7V = 20mA x R

7/0.02 = R

R = 350 ohms

The last step is to find a resistor with a value equal to or close to but greater than the value determined via Ohm’s law.


  • Low power consumption.
  • Long life (100 000hrs).
  • Low heat emissions.
  • Eco-friendly and much less toxic.


  • More expensive per lumen than normal filament bulbs.
  • Temperature dependant for performance and light quality:
    • Performance and light quality is better at lower temperatures.
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