Many AC resistive circuits such as heating elements and lamps consist of a pure ohmic resistance only and have negligible values of inductance or capacitance adding to its impedance. In such circuits we can use both Ohms Law and Kirchoff’s laws as well as simple circuit rules for calculating the voltage, current, impedance and power as we would in DC circuit analysis. When working with such rules it is usual to use rms values only.
Z = R
Z = R + j0