Question

In the given circuit, the breakdown voltage of the Zener diode is 3.0 V. What is the value of Iz ?

• A. 7 mA
• B. 1.5 mA
• C. 5.5 mA
• D. 10 mA

Answer 1

Answer: (C)

5.5 mA

Answer 2

Step 1: Identify the Zener Breakdown Voltage

Given $V_Z = 3 \, \text{V}$.

Step 2: Determine the Potentials in the Circuit

Let the potential at point $B = 0 \, \text{V}$. The potential at $E(V_E) = 10 \, \text{V}$. Therefore, $V_C = V_A = 3 \, \text{V}$ across the Zener diode.

Step 3: Calculate the Total Current $I$

Using Ohm’s law, the total current $I$ through the $1 \, \text{k}\Omega$ resistor:

$I = \frac{10 - 3}{1000} = \frac{7}{1000} = 7 \, \text{mA}$

Step 4: Find $I_1$, the Current through the $2 \, \text{k}\Omega$ Resistor

Voltage across the $2 \, \text{k}\Omega$ resistor is $3 \, \text{V}$:

$I_1 = \frac{3}{2000} = 1.5 \, \text{mA}$

Step 5: Calculate $I_Z$, the Zener Current

By Kirchhoff’s Current Law (KCL), $I = I_Z + I_1$:

$I_Z = I - I_1 = 7 \, \text{mA} - 1.5 \, \text{mA} = 5.5 \, \text{mA}$

So, the correct answer is: 5.5 mA