Question

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

• A. $10mA$
• B. $15mA$
• C. $20mA$
• D. $5mA$

Answer 1

The correct option is D $5mA$

For $R=1k\Omega$
$i_1=\frac{15}{1}mA=15mA$
$R=250\Omega$
$i_{250}=\frac{20-15}{250}=\frac{5}{250}=20mA$
$i_{Zener}=20-15=5mA$