JEE Mains · Physics · STD 12 - 14. Semicondutor electronics
A potential divider circuit is connected with a DC source of \(20 \mathrm{~V}\), a light emitting diode of glow in voltage \(1.8 \mathrm{~V}\) and a zener diode of breakdown voltage of \(3.2 \mathrm{~V}\). The length (PR) of the resistive wire is \(20 \mathrm{~cm}\). The minimum length of \(P Q\) to just glow the LED is _______ cm.
- A 2
- B 3
- C 4
- D 5
Answer & Solution
Correct Answer
(D) 5
Step-by-step Solution
Detailed explanation
\(PR=20cm\) \(\mathrm{~V}_{\mathrm{PQ}}=\frac{1}{4} \times \mathrm{R}_{\mathrm{PR}}\) \(\ell_{\min }(\mathrm{PQ})=\frac{1}{4} \times 20\) \(=5 \mathrm{~cm}\)
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