Given, Zener diode voltage, Vz=30V Supply voltage, V=90V According to figure,
Let I be supply current, then I2 be Zener current (=I−I1) and I1 be current through 5kΩ. ∴‌‌V1=V2=30V By Ohm's law, ‌‌V1=V2=I1R ⇒‌‌I1=V2∕R=‌
30
5000
=6mA If V′ be the voltage across 4kΩ resistor. ∴‌‌V′=90−30=60V and I=‌