Question:

A Zener diode, having breakdown voltage equal to 15 V, is used in a voltage regulator circuit. The current through the diode is?

20 mA

10 mA

5 mA

15 mA

Voltage across zener diode is constant (15V).
Current through 1kΩ resistor = 15V / 1kΩ = 15 mA