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). Z = √(R² + (XL - XC)²); below f₀, XC dominates and falls with f, so Z decreases. At f₀, XL = XC and Z = R (minimum). Above f₀, XL dominates and rises with f, so Z increases. So the answer is (d).

With gradual increase in frequency of an a.c. supply, the impedance… | MHT CET 2024 (11 May, Shift 1)

Q45MHT CET 2024 · 11 MAY · 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)

$Z = \sqrt{R^2 + (X_L - X_C)^2}$ ; below $f_0$ , $X_C$ dominates and falls with $f$ , so $Z$ decreases.
At $f_0$ , $X_L = X_C$ and $Z = R$ (minimum).
Above $f_0$ , $X_L$ dominates and rises with $f$ , so $Z$ increases.
So the answer is (d).

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