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 i s ________ Ω.
Physics · semiconductor · application of diode and zener breakdown
JEE Mains 2026 24 January Morning Shift

Question

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 i s ________ Ω.

Physics · semiconductor · application of diode and zener breakdown

JEE Mains 2026 24 January Morning Shift

G1 Physics · Accepted Answer

Maximum allowed Zener current is obtained from P(max) = V(Z)I(max). Given, P(max) = 0.4 W, V(Z) = 10 V. Therefore, I(max) = 0.4/10 = 0.04 A. The protective resistor has voltage drop V(R) = 15-10 = 5 V. Hence, R = V(R)/I(max) = 5/0.04 = 125 Ω. Therefore the answer is 125.