Q 12-14-166JEE MainJEE Main 2020 (9 Jan, Shift 2)Medium
The circuit shown below is working as an $8$ V dc regulated voltage source. When $12$ V is used as an input, the power dissipated (in mW) in each diode is (considering both zener diodes are identical)
Numerical value type. Enter your answer.
Answer: 40
The two identical zeners share the $8$ V output, so each has $4$ V across it.
The two $200\ \Omega$ resistors are in series with the zeners and drop $12 - 8 = 4$ V:
$$I = \frac{4}{400} = 10\ \text{mA}$$
No load is connected, so the whole $10$ mA flows through the zeners:
$$P = 4\times10\times10^{-3} = 0.04\ \text{W} = 40\ \text{mW}$$
Solution by Sreeraj P, M.Sc Physics