We know that, If a voltage `V = V_0 sinomegat` applied to a series RLC circuit,
current in the circuit given by `I = I_0 sin(omegat + phi)` where

`I_0 = V_0/Z` and `phi = tan((X_C -X_L)/R)`

Then the average power over a cycle is given by

`barP = V_0/sqrt2 I_0/sqrt2 cosphi`

`= I_(rms)^2 Z cosphi`

The quantity `cosphi` is called the power factor, If the circuit contains only an inductor or capacitor, we know that the phase difference between voltage and current is `pi/2.` Therefore, power factor will be zero.

`cosphi = 0,`

`bar P = 0`

so no power is dissipated even though a current is flowing in the circuit. This phenomenon of current is referred as watt less current.
So in a circuit having Impedance Watt less current `I = I_0 sinphi` .