Let's think in an AC circuit consist in a resistor R in series with a capacitor C connected to the power grid, inverter or any AC voltage power source of Amplitude V and frequency w

 But the resistor is not common, it changes his resistance according to this:

R(i)= k/i

As R dont can get negative values we can use the absolute value of i

R(i)= k/abs(i)

So resistance increases if current decrease and resistance decrease if current increases

Then the equation of the circuit is:


V*sen(w*t)= R*i + 1/C*q

V*sen(w*t)= k + 1/C*q

Where q is the charge in the capacitor

Solving this single equation for get the current:

i= dq/dt=C*V*w*cos(w*t)

Is the same solution for the case the voltage in the resistor is -k when current value is negative

So we can see current is at 90 degrees of phase shift from voltage, the power source see reactive pure power , the power source dont see the resistor, it vanishes because in the resistor there is a DC voltage
 
 This explain how some free energy devices  works as the "scalar charger" is a capacitor in series with a diode bridge has the battery connected to the positive and negative terminals of the bridge, this series circuit is connected direct to the power grid. A resistive load can be connected in parallel to the battery to make measurements of input and output power