A series RLC circuit is connected to an AC source whose frequency can be varied over…
PHYSICS · Multi-part · CBSE · Physics · Alternating Current · Alternating Current
Problem
A series RLC circuit is connected to an AC source whose frequency can be varied over a wide range. Let the resistance, inductance and capacitance of the circuit be R, L and C respectively.
(i) Write the mathematical expression for the phase angle ϕ between the source voltage and the circuit current in terms of R, the inductive reactance XL and the capacitive reactance XC.
(ii) Explain qualitatively how the sign (positive or negative) of ϕ depends on whether the driving frequency is below, equal to or above the resonant frequency of the circuit.
(iii) For a frequency that is much lower than the resonant frequency, state clearly which quantity (current or voltage) leads and which lags. Give a brief reason.
(iv) Draw a neat, labelled sketch showing the variation of ϕ with angular frequency ω in the neighbourhood of resonance, indicating the regions of lead and lag on your graph.