Question
The following diagram shows a Zener diode as a voltage regulator. The Zener diode is rated at $V_{Z} = 5\text{ }V$ and the desired current in load is 5 mA . The unregulated voltage source can supply upto 25 V . Considering the Zener diode can withstand four times of the load current, the value of resistor $R_{S}$ (shown in circuit) should be $\_\_\_\_$ $\Omega$.
Options
Solution
Vz = 5 V
IL = 5 mA
Vin(max) = 25 V
Zener can carry max current = 4 × 5 mA = 20 mA
Worst case (no load, IL = 0): All current through Zener → Iz = 20 mA Voltage across Rs = 25 – 5 = 20 V
Rs = 20 V / 20 mA = 1000 Ω
NTA officially dropped this question (JEE Main 2026, 23 Jan Shift-I). The stored answer (1000 Ω) is rigorously sound. Original NTA status: Dropped.
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