With inductive reactance, the phase shift that
is induced where voltage leads current by
90 degrees or pi/2 radians, is the
voltage of the self-induced emf vs'
the current from our applied voltage?
An inductance opposes a change in current, and a capacitor opposes a
change in voltage.
When you first apply a voltage to an inductor, the current begins to
rise, as the voltage decreases due to series resistance in the supply,
or by design in your circuit. (the series resistance drops more voltage,
leaving less for the inductor.)
When you feed that circuit with AC, the result turns out to be a 90 degree
phase lag for the current. i.e., when you change the applied voltage, the
current doesn't change right away, like it does with a resistor.
A capacitor is just the opposite - try to apply a voltage to it, and for
a very short time it looks like a short circuit - the current first goes
as high as it can, and the voltage can follow it as it looks less like
a short circuit - ergo, the voltage lags the current in/on a cap.
Hope This Helps!
Rich