Question

A device X is connected across an ac source of voltage V = Vo sin ωt. The current through X is given as 

I=I₀ sin(ωt+π/2).

(a) Identify the device X and write the expression for its reactance.

(b) Draw graphs showing variation of voltage and current with time over one cycle of ac, for X.

(c) How does the reactance of the device x vary with frequency of the ac ? Show this variation graphically.

(d) Draw the phasor diagram for the device X.

Answer 1

(a) The device is a capacitor. The reactance of the capacitor is given by

(b) Graph of voltage and current w.r. to time

(c) Graph showing the variation of Xc with frequency f

(d) Phase diagram for device X is shown in fig.