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

10 mA 15 mA 20 mA 5 mA

5 mA

Voltage across Zener diode is constant. Current in 1kΩ resistor. $(i)_{1kΩ}\frac{15volt}{1kΩ}=15mA$ Current in 250Ω resistor, $(i)_{250Ω}=\frac{(20-15)V}{250Ω}=\frac{5}{250Ω}$ $=\frac{20}{1000}A=20mA$ $∴(i)_{zener\, diode} = (20 −15) = 5mA$