The line that draws power supply to your house from street has

Question

$\begin{array}{1 1} \text{zero average current} \\ \text{220 v average voltage} \\ \text{voltage and current possibly differing in phase} 90^{\circ} \\ \text{voltage and current possibly differing in phase} \phi \;such \;that\;|\phi | < \large\frac{\pi}{2} \end{array}$