- If a circuit consisted of a resistor R parallel with a capacitor C is given an external current excitation with frequency of ω, let the current equals to I0*exp(jωt), what is the response of voltage E? Would the impedance equals to R(1-ωCRj)/(1+ω^2*C^2*R^2), the same as the case when the circuit is excited by AC voltage E0*exp(jωt)?