The resonant frequency for the given circuit will be

The $$R-L-C$$ series circuit shown is supplied from a variable frequency voltage source. The admittance $$-$$ locus of the $$R-L$$ $$-C$$ network at terminals $$AB$$ for increasing frequency $$\omega $$ is

In the figure given below, all phasors are with reference to the potential at point $$''O''.$$ The locus of voltage phasor $${V_{YX}}$$ as $$R$$ is varied from zero to infinity is shown by

The circuit shown in the figure is energized by a sinusoidal voltage source $${V_1}$$ at a frequency which causes resonance with a current of $${\rm I}$$.

The phasor diagram which is applicable to this circuit is