Which of the following combinations should be selected for better tuning of an L-C-R circuit used for combination? (a) R = 20 Ω, L = 1.5 H, C = 35 μ F (b) R = 25 Ω, L = 2.5 H, C = 45 μ F (c) R = 15 Ω, L = 3.5 H, C = 30 μ F (d) R = 25 Ω, L = 1.5 H, C = 45 μ F

Answer: (c). Better tuning means a sharper resonance, i.e. a larger Q = 1/R√(L/C). (a) 1/20√1.535×10⁻⁶ ≈ 10.4; (b) 1/25√2.545×10⁻⁶ ≈ 9.4 (c) 1/15√3.530×10⁻⁶ ≈ 22.8; (d) 1/25√1.545×10⁻⁶ ≈ 7.3 So the answer is (c) R = 15 Ω, L = 3.5 H, C = 30 μ F.

Which of the following combinations should be selected for better… | NEET 2016 (Phase 2)

Q104NEET 2016 · PHASE 2Easy

Resonance, Bandwidth & Q Factor

Which of the following combinations should be selected for better tuning of an L-C-R circuit used for combination?

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Answer: (c)

Better tuning means a sharper resonance, i.e. a larger $Q = \frac{1}{R}\sqrt{\frac{L}{C}}$ .
(a) $\frac{1}{20}\sqrt{\frac{1.5}{35\times10^{-6}}} \approx 10.4$ ; (b) $\frac{1}{25}\sqrt{\frac{2.5}{45\times10^{-6}}} \approx 9.4$
(c) $\frac{1}{15}\sqrt{\frac{3.5}{30\times10^{-6}}} \approx 22.8$ ; (d) $\frac{1}{25}\sqrt{\frac{1.5}{45\times10^{-6}}} \approx 7.3$
So the answer is (c) $R = 15\ \Omega$ , $L = 3.5$ H, $C = 30\ \mu$ F.

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