1. An electrical element X, when connected to an alternating voltage source, has the current through it leading the voltage by π/2 rad. Identify X and write an expression for its reactance.

2. Draw the graphs showing the variation of reactance of (a) a capacitor and (b) an inductor with the frequency of an a.c. circuit

As has the current through it leading the voltage by π/2 rad, the electric element X is a capacitor.

Its expression for reactance

X_c = 1/Cω = 1/2πCf Where C = capacitance, ω = angular frequency and f = frequency

X_L = Lω = 2πLf

Thus variance of inductive reactance with frequency is linear.

Thus variance of capacitative  reactance with frequency is rectangular hyperbolic.