A series \(R L C\) circuit has \(R=18 \mathrm{k} \Omega, C=14 \mu \mathrm{F},\) and \(L=0.20 \mathrm{H}\) (a) At what frequency is its impedance lowest? (b) What's the impedance at this frequency?

Short Answer

Expert verified
The impedance is lowest at the resonant frequency, which is approximately 849.83 Hz, and the impedance at this frequency is \(18k\Omega\).

Step by step solution

01

Calculate Resonant Frequency

To find the frequency at which the impedance is lowest (resonant frequency), we can use the formula:\[f=\frac{1}{2 \pi \sqrt{L C}}\]where \(L\) is the inductance, \(C\) is the capacitance. In this problem, \(L = 0.20H\) and \(C = 14\mu F = 14 \times 10^{-6} F\). Substitute the values of \(L\) and \(C\) in the formula and calculate the resonant frequency.
02

Calculate Impedance at Resonant Frequency

At resonant frequency, the reactance (X) of inductor (XL) equals the reactance of capacitor (XC), i.e, \(X_{L}=X_{C}\). The impedance (Z) of the circuit at this frequency is given by Ohm's law:\[Z=\sqrt{R^2+ (X_L - X_C)^2}\]Because \(X_{L} = X_{C}\) at resonance, the impedance (Z) equals the resistance (R) of the circuit. Therefore, the impedance Z at the resonant frequency in this problem is \(Z = R = 18k\Omega\).

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