Given, power, P=2W Zener breakdown voltage, Vz=10V Voltage range, (V1 to V2)=6V and 14V Let resistance be R. Since, ‌‌P=VIz Zener current, ‌‌Iz=‌
P
Vz
=‌
2
10
=0.2A For safe operation of Zener diode, Iz=Is‌‌=0.2A ∴‌‌V2−Vz‌‌=IsRs ⇒‌‌14−10‌‌=IsRs ⇒‌‌Rs‌‌=‌