1. Why is a buzzer used in a circuit?
A buzzer is an audio signal device, which may be mechanical, electromechanical, or piezoelectric (piezo for short). Typical uses of buzzers in the industry is as an alarm devices, which makes a buzzing or beeping noise while need buzzing.

2. What is a piezoelectric buzzer?
A piezoelectric buzzer, which is a flat piece of piezoelectric material with two electrodes. This type of buzzer requires some kind of oscillator (or something more complicated like a microcontroller) to drive it, if you apply a DC voltage you will just get a click. They are used in places where you need something that emits an audible tone, but don’t care about high-fidelity sound reproduction, like microwave ovens, smoke alarms, and electronic toys.

3. How do you make a buzzer?
You need electronic knowledge and prepare some raw materials in advance. The working principle of buzzer is the vibrating disk in a magnetic buzzer is attracted to the pole by the magnetic field. When an oscillating signal is moved through the coil, it produces a fluctuating magnetic field which vibrates the disk at a frequency equal to that of the drive signal.

4. Does buzzer have polarity?
A buzzer has Positive and Negative Polarity. As for active buzzers which have positive and negative polarity, they can make sound when voltage signal is effected on the pin feet. However, active buzzers are with single tone and constant frequency.