A student is studying a series RLC circuit connected to an AC source whose frequency…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A student is studying a series RLC circuit connected to an AC source whose frequency can be varied. The circuit contains a fixed resistor, a fixed inductor and a variable capacitor.
(a) State the condition under which the circuit is said to be in resonance.
(b) Explain, with reasons, how the impedance of the circuit and the rms current through it change as the supply frequency is swept from well below to well above the resonant frequency.
(c) The values of the fixed components are R=50Ω and L=0.20H. If the supply frequency is 50Hz, describe qualitatively whether the student must increase or decrease the capacitance from a very small initial value to achieve resonance. Also explain how the phase angle between current and voltage varies during this adjustment.