In an L.C.R. series a.c. circuit, the current

$\tan \text{ϕ}=\frac{V_C-V_L}{V_R}\left(if{V}_C>V_L\right)$

$\mathrm{tan\varphi }=\frac{V_L-V_C}{R}\left(if{V}_L>V_C\right)$

where $\text{ϕ}$ is angle between current and applied voltage and $V_L, V_C, V_R$ are the inductor voltage, capacitor voltage and resistor voltage respectively.

Depending upon the value of $\text{ϕ}$ the current lags or leads or is in phase with the generator voltage.