Question

The circuit shown in the figure below will act as an ideal source with respect to terminal A and B when the frequency is ___________

(a) Zero

(b) 1 rad/s

(c) 4 rad/s

(d) 16 rad/s

The question was posed to me by my college professor while I was bunking the class.

My question comes from Advanced Problems on Resonance in section Resonance & Magnetically Coupled Circuit of Network Theory

Answer 1

The correct answer is (c) 4 rad/s

To explain: Z(s) t = \(\frac{(Ls)\frac{1}{Cs}}{Ls + \frac{1}{Cs}} = \frac{Ls}{LCs^2+1} \)

Putting s = jω, we get, Z (jω) = \(\frac{jωL}{1 -LCω^2} \)

For ideal current source, Z (jω) = ∞

Or, 1 – LCω^2 = 0

Or, ω = \(\frac{1}{\sqrt{LC}} = \frac{1}{\sqrt{\frac{1}{16}×1}}\) = 4 rad/s.