 The phase of the voltage across a purely reactive device (a capacitor with an infinite resistance or an inductor with a resistance of zero) "lags" the current by formula_48 radians for a capacitive reactance and "leads" the current by formula_48 radians for an inductive reactance.Without knowledge of both the resistance and reactance the relationship between voltage and current cannot be determined.The origin of the different signs for capacitive and inductive reactance is the phase factor formula_50 in the impedance.