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
Answer & explanation
Correct answer: option 4
Voltage across Zener diode is constant.
Current in 1kΩ resistor.
$(i)_{1kΩ}\frac{15volt}{1kΩ}=15mA$
Current in 250Ω resistor,
$(i)_{250Ω}=\frac{(20-15)V}{250Ω}=\frac{5}{250Ω}$
$=\frac{20}{1000}A=20mA$
$∴(i)_{zener\, diode} = (20 −15) = 5mA$