A series LCR circuit is at resonance. The capacitance is changed from C to 4C while the source frequency remains fixed. Which statements are correct in the new steady state?
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Question

A series LCR circuit is at resonance. The capacitance is changed from C to 4C while the source frequency remains fixed. Which statements are correct in the new steady state?

G1 Physics · Accepted Answer

At fixed frequency, Xᴄ = 1/(ωC), so C→4C makes Xᴄ→Xᴄ/4. Xʟ=ωL is unchanged. Initially Xʟ=Xᴄ; therefore after the change Xʟ>Xᴄ, making the circuit inductive. The impedance becomes greater than R, so current decreases.