Final answer:
A diac acts like two diodes in series and is primarily used as a triggering device for other semiconductors. It allows electric current to flow in only one direction through a p-n junction.
Step-by-step explanation:
A diac acts like two diodes in series; therefore, it is primarily used as a triggering device for other semiconductors. A diode is a circuit element that allows electric current to flow in only one direction. When a p-n junction is formed, electrons from the conduction band of the n-type material diffuse to the p-side, where they combine with holes in the valence band. This migration of charge leaves positive ionized donor ions on the n-side and negative ionized acceptor ions on the p-side, producing a narrow double layer of charge at the p-n junction called the depletion layer.