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

• A

  $10 \mathrm{~mA}$
• B

  $15 \mathrm{~mA}$
• C

  $20 \mathrm{~mA}$
• Correct answer
  D

  $5 \mathrm{~mA}$

Solution

For I $1 \mathrm{k} \Omega$ $$ i_1=\frac{15}{1}=15 \mathrm{~mA} $$ For II $250 \Omega$ $$ \begin{aligned} & i_{250 \Omega}=\frac{20-15}{250}=\frac{5}{250} \\ &=\frac{20}{1000}=20 \mathrm{~mA} \\ & \therefore \quad i_{\text {zener }}=20-15=5 \mathrm{~mA} \end{aligned} $$

Hence, the correct answer is option: 'D'.