Zener diode is used to

• A. Sense voltage change
• B. Rectify AC
• C. Store charge
• D. Amplify signal

Answer: (A)

A Zener diode is used to sense and regulate voltage levels. When reverse-biased, it reaches a well-defined breakdown voltage and then clamps the voltage across itself, keeping it around that Zener voltage even as the input or load current changes. That behavior lets the circuit “sense” when the voltage has reached a specific value and maintain a stable reference or output. It’s not used to rectify AC, store charge, or amplify signals, which are functions of other components.