AP EAMCET · PHYSICS · Semiconductors

A Zener diode voltage regulator operated in the range \(120 \mathrm{~V}-180 \mathrm{~V}\) produces a constant supply of \(110 \mathrm{~V}\) and \(250 \mathrm{~mA}\) to the load. If the maximum current is equally shared between the load and the Zener diode, then the values of load resistance \(\left(R_L\right)\) and series resistance \(\left(R_S\right)\) are respectively

A \(R_L=280 \Omega, R_S=70 \Omega\)
B \(R_L=440 \Omega, R_S=140 \Omega\)
C \(R_L=70 \Omega, R_S=280 \Omega\)
D \(R_L=440 \Omega, R_S=1400 \Omega\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(R_L=440 \Omega, R_S=140 \Omega\)

Step-by-step Solution

Detailed explanation

We have, \(R_L=\frac{V_L}{I_L}=\frac{110}{250 \times 10^{-3}}=440 \Omega\) As current is equally shared by Zener diode and resistance \(R\). So, \(I_Z=250 \mathrm{~mA}\) Then, \(I=2 \times 250=500 \mathrm{~mA} \quad\left[\because I=I_L+I_Z\right]\) \(=0.5 \mathrm{~mA}\) So,…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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