For the circuit shown below, calculate the value of  $I_Z:$

In the given circuit, the zener diode is used as a voltage regulating device. Hence, the voltage across $2000\Omega$ is 30 V.

Current flowing through $1000\Omega ,I=\frac{100-50}{1000}=50mA$

Current flowing through $2000\Omega ,I\text{'}=\frac{50}{2000}=25mA$

Using Kirchhoff’s current law, $I=I_2=I\text{'}\Rightarrow I_Z=I-I=50-25=25mA$