Question

A Zener diode is connected to a battery and a load as shown. The currents $I$, $I_Z$ and $I_L$ are respectively

• A. $12.5mA,5mA,7.5mA$
• B. $15mA,7.5mA,7.5mA$
• C. $15mA,7.5mA,5mA$
• D. $12.5mA,7.5mA,5mA$

Answer 1

The correct option is D $12.5mA,7.5mA,5mA$

As long as the $V_{in}$ is greater than the zener Voltage $10V$, the zener is in breakdown region and hence the voltage across the load remains constant. The series limiting resistance $4k\Omega$ limits the input current.
Current in load $I_L=\frac{10}{2\times {10}^3}=5mA$
Voltage drop across the $4k\Omega$ is $60-10=50V$
Hence $I=\frac{50}{4\times {10}^3}=12.5mA$
Hence, $I_Z=I-I_L=12.5-5=7.5mA$