A voltage regulating circuit consisting of Zener diode, having break-down voltage of 10 V and maximum power dissipation of 0.4 W, is operated at 15 V. The approximate value of protective resistance in this circuit is ______ Ω.
Answer: 125
Solution
At the rated limit the Zener dissipates PD=VZIZ, so IZ=100.4=0.04 A. The series protective resistor carries this current and drops the surplus voltage 15−10=5 V, so R=0.0415−10=125. The protective resistance is about 125Ω.
JEE Main · 2026 · 24 Jan 2026 · Shift 1 · Integer answer