10 – Light Emitting Diode

The picture shows a sketch of a Light Emitting Diode (LED) on the left and the symbol on the right.

A light emitting diode is an electronic component and semiconductor light source. The two terminals are called the anode (the arrow side) and the cathode (the bar side). An LED has the property to create light when current pass in one direction from the anode to the cathode but it blocks current flowing in the other direction from the cathode to the anode and no light is created in this direction. The arrow in the symbol points in the opposite direction as electron flow because it was based on conventional current flow before the discovery of electrons. In other words current will flow through the LED if the anode (arrow side) is positive and the cathode (bar side) is negative. 

LED’s are available in various colours including the visible, ultraviolet and infrared wavelengths.

LED’s are widely used in everyday life and the following is a few application examples:

  1. Indicator lamps in electronic devices.
  2. Infrared remote controls.
  3. Motorcar breaklights and indicators, traffic lights and other lighting applications.