requiring the AC (Alternating Current), whether in home、schools or other place . AC of the very important system in our live .  now the led even quotes Alternating Current.
The work currently is moving toward a certainty direction, when turn-on forware voltage increase. toward currently by making led work. the work currently is flowing the other way when turn-on reverse voltage increase. and you will see them on the other side of the led to generate light.