With gradual increase in frequency of an a.c. supply, the impedance of an LCR series circuit (a) increases (b) decreases (c) remains constant (d) first decreases, becomes minimum and then increases

Answer: (d). Zff₀RZ min = R Z = √(R² + (XL - XC)²) with XL = 2π f L and XC = (1)/(2π f C). Below f₀, XC dominates and falls as f rises, so Z decreases. At f₀, Z = R (minimum); above f₀, XL dominates and Z increases. So the answer is (d).

With gradual increase in frequency of an a.c. supply, the impedance… | MHT CET 2026 (16 Apr, Shift 1)

Q14MHT CET 2026 · 16 APR · SHIFT 1Easy

Resonance, Bandwidth & Q Factor

With gradual increase in frequency of an a.c. supply, the impedance of an LCR series circuit

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Answer: (d)

$Z = \sqrt{R^2 + (X_L - X_C)^2}$ with $X_L = 2\pi f L$ and $X_C = \dfrac{1}{2\pi f C}$ .
Below $f_0$ , $X_C$ dominates and falls as $f$ rises, so $Z$ decreases.
At $f_0$ , $Z = R$ (minimum); above $f_0$ , $X_L$ dominates and $Z$ increases.
So the answer is (d).

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