180. Referring to figures «C» and «D» of the illustration what is the phase relationship of current to voltage in a purely resistive circuit

In a purely resistive AC circuit, the current and voltage are in phase because the resistor introduces no phase shift. Ohm's law dictates that the instantaneous current is directly proportional to the instantaneous voltage, resulting in simultaneous peaks, troughs, and zero crossings. Figures C and D illustrate this alignment, confirming that the current is in phase with the applied voltage.