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

Answer 1

The correct option is B $5mA$

Voltage drop across $250\Omega =20-15=5V$

$\therefore$ Current through $250\Omega =\frac{5}{250}=\frac{1}{50}A=20mA$

Current through the $1k\Omega$ resistance

$=\frac{15V}{1000\Omega }=15\times {10}^{-3}A=15mA$

$\therefore$ Current through the diode
$=(20–15)=5mA$.