What is the phase difference between ac emf and current in the following ?
I) pure resistor II) pure inductor III) pure capacitor

I) In a pure resistor there is no phase difference between ac emf and current
II) In a pure inductor the current lags behind e.m.f by $\frac{\mathrm{\pi }}{2}$ radian or 90°
III) In a pure capacitor the current is ahead of the emf applied across it by $\frac{\mathrm{\pi }}{2}$ radian or 90°