ARRL Technician Practice Exam 2025 - Free Technician License Practice Questions and Study Guide

Transistors are a class of electronic components specifically designed to control current flow using a voltage or current signal. They act as switches or amplifiers in electronic circuits, allowing a small input signal to control a larger output signal. This characteristic makes transistors fundamental in signal processing, switching applications, and various electronic circuits where modulation of current or voltage is necessary.

In contrast, diodes are primarily used for directing current flow in one direction and do not control the current flow based on a signal. Capacitors store electrical energy and release it when needed but do not control current flow based on a signal. Resistors manage current flow by providing resistance but do not have the ability to modulate current flow based on a control signal. Hence, transistors are unique in their functionality, being able to effectively utilize voltage or current signals to influence the current flowing through them, making them the correct answer.