What is the magnitude of the current at the input of a parallel RLC circuit at resonance?
Why In a parallel RLC circuit at resonance the inductive and capacitive branch currents are equal in magnitude but opposite in phase, so they cancel each other and circulate within the tank instead of being drawn from the source. What is left for the source to supply is only the current through the resistive element, so the circuit looks like a very high impedance and the input current drops to its lowest value. Parallel resonance means maximum impedance, therefore minimum line current.
Watch out Maximum current is what happens in a series RLC circuit at resonance, where the reactances cancel and leave only the small series resistance. R/L and L/R are time-constant style ratios and have nothing to do with resonant current.
Parallel = high Z = low current in; series = low Z = high current. Opposite twins.