What function does a diode serve in an electrical circuit?

A diode is a semiconductor device that primarily serves to allow current to flow in only one direction. This unidirectional flow is crucial in many electronic applications. When forward-biased, the diode has low resistance and conducts electrical current, while in reverse bias, it presents high resistance and effectively blocks the current.

This property is essential for various functionalities in circuits, such as rectification, where alternating current (AC) is converted to direct current (DC). By ensuring that current flows in one direction, diodes protect sensitive components from damage that could occur if current were allowed to flow backwards. Thus, the diode plays a fundamental role in controlling the direction of current flow in electrical circuits, which is why the answer regarding its function is correct.