Discuss the phasor diagram of an a.c circuit with a pure resistance only.

If the input voltage $V_{\mathrm{i}}$ to the circuit below is given by $V_{\mathrm{i}}\left(t\right)=A\cos \left(2\pi ft\right)\text{,}$ the output voltage is given by $V_{\mathrm{o}}\left(t\right)=B\cos \left(2\pi ft+\varphi \right)$.

Which one of the following four graphs best depict the variation of $\varphi$ vs $f$?

The phaser diagram of the alternating voltage across an unknown device $\mathrm{X}$ and current flowing through it are shown below.

Draw the graphical variation of current and voltage with $\mathrm{\omega t}$ through this device.

A parallel combination of pure inductor and capacitor is connected across a source of alternating EMF $e$. The currents flowing through an inductor and capacitor are $i_L$ and $i_C$ respectively. In this parallel resonant circuit, the condition for currents $i$ $,i_L$ and $i_C$ is ($i=$net RMS current in the circuit)