What is the primary function of a diode?

The primary function of a diode is to allow current to flow in one direction only. This characteristic is fundamental to the operation of diodes, making them essential components in various electronic circuits. When a diode is forward-biased (with the anode connected to a higher voltage than the cathode), it conducts current, allowing current to flow through. Conversely, when it is reverse-biased (the anode is at a lower voltage than the cathode), it blocks current flow, effectively acting as a one-way gate for electrical current.

This unidirectional flow is crucial in many applications, such as rectifying alternating current (AC) into direct current (DC), where diodes are used to convert AC, which flows in both directions, into a form that flows consistently in one direction. This function is foundational in power supply circuits, signal processing, and many other electronic applications where controlling the direction of current flow is necessary for the intended function of the circuit.

In contrast, the other options describe functions that do not align with the primary role of a diode. For example, amplifying signals pertains to devices like transistors, providing resistance relates to resistors, and allowing current to flow in both directions contradicts the fundamental operating principle of a diode