Actuator: LED

LEDs (Light Emitting Diodes) are small lights made from a semiconductor material and metal wire. They light up when electrical current passes through them. LEDs can be different colors that depend on the energy it gives off and how far electrons cross a gap inside the LED. Because LEDs have a positive end and a negative end, they have polarity and will only light up in a circuit when placed in the direction of electrical current flow. Because LEDs transfer energy (battery) to another form of energy (excited electrons and photons), it is an example of an actuator. In your light, which side is ‘positive’? What happens when you switch its direction in the circuit?

What is an L.E.D.?
The illuminating physics behind LED lights