What is the function of a diode?

The function of a diode is to act as a check valve that restricts current to flow in one direction. This is a fundamental characteristic of diodes, as they allow current to pass through them when forward-biased (when the positive side is connected to the anode and the negative side to the cathode) while blocking current when reverse-biased. This behavior is crucial in various applications, such as rectifying alternating current (AC) to direct current (DC) in power supplies, protecting circuits from reverse polarity, and more.

Other options touch on different electronic functions but do not pertain to the fundamental role of a diode. For example, amplifying electrical signals involves components like transistors rather than diodes. Measuring electrical resistance is typically done using specialized devices like ohmmeters. Increasing current flow is generally managed with power amplifiers or current sources, not diodes. Understanding the unique role of a diode is essential in grasping basic electronic principles and circuit design.