If the light is absorbed into the cell, the light's energy is transferred to the electrons in the semiconductor. This causes the electrons to flow, creating an electrical current. Diodes are semiconductors that allow electricity to flow in one direction but not the other like a one way valve for electricity. The positive side of the diode is called the anode . The negative side is called the cathode .
Current always flows from the anode to the cathode.
The two small arrows pointing away from the diode represent light energy being emitted. Sketch a picture of each arrangement that makes the LED glow. Compare your sketches with series and parallel circuits below.