The following diagram shows a Zener diode as a voltage regulator. The… | JEE Main 2026 (23 Jan, Shift 1)

Q12JEE Main 2026 · 23 JAN · SHIFT 1Medium

Special Purpose Diodes

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 $\underline{\qquad\quad}\ \Omega$ .

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Answer: (c)

Worst case is the maximum input $25$ V, giving drop $25 - 5 = 20$ V across $R_s$ .
Safe current limit: $4 I_L = 4 \times 5 = 20$ mA, taken as the current through $R_s$ .
$R_s = \frac{20}{20 \times 10^{-3}} = 1000\ \Omega$
So the answer is (c) $1000\ \Omega$ .

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