Question

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

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

Answer 1

The correct option is A $5mA$

Here, zener diode is connected parallel to the $1k\Omega$ so the voltage across $CD$ will be equal.
Let current $i$ be flowing between point $A$ and $B$

now calculating current as $i$=$\frac{20-15}{250}=20mA$
Now $i_2=\frac{15-0}{1000}=15mA$
By using Junction rule at point $B:$
$i=i_1+i_2{i}_1=i-i_2{i}_1=20-15=5mA$

Hence, option $A$ is correct.