A passive buzzer is an electronic component that produces sound when an alternating current (AC) signal is applied to it. Unlike active buzzers, which have built-in oscillators, passive buzzers require an external signal to generate sound. They are often used in various applications, such as alarms, timers, and toys, where sound alerts are needed. These buzzers typically consist of a diaphragm and a coil, which vibrate to create sound waves. The frequency of the sound produced depends on the frequency of the AC signal applied. Passive buzzers are commonly found in devices like microcontrollers, Arduino projects, and alarm systems.