Q 12-14-149JEE MainJEE Main 2021 (22 Jul, Shift 1)Medium
In a given circuit diagram, a 5 V zener diode along with a series resistance is connected across a 50 V power supply. The minimum value of the resistance required, if the maximum zener current is 90 mA will be ______ $\Omega$.
Numerical value type. Enter your answer.
Answer: 500
The Zener current is largest when the load draws no current, so then all the current through $R$ passes through the Zener:
$$I_{max} = \frac{50 - 5}{R} \le 90\ \text{mA} \Rightarrow R \ge \frac{45}{0.09} = 500\ \Omega$$
Solution by Sreeraj P, M.Sc Physics