A set of elements is subjected to a voltage v = 60 cos (5t + 45º) V and passed through by a current i = 3 cos (5t + 15º) A.

Question

In sinusoidal steady state, the set of elements is represented by an impedance whose imaginary part is

(A) 35Ω .

(B) 25Ω .

(C) 20Ω .

(D) 15Ω .

(E) 10Ω .

Answer 1

This is an AC Steady State Analysis.

Transition voltage from time domain to phasor

V=60V ∠45^o

Transition current from time domain to phasor

I=3A ∠15^o

Use Impedance Form of Ohm's Law

Z=V/I=60V ∠45^o /3A ∠15^o =20Ω∠30^o=20*Cos(30^o)+j(20*Sin(30^o))=17.3Ω +j(10Ω)

The real part of the impedance is 17.3Ω.

The imaginery part of the impedance is 10Ω

The Answer is E, The imaginery part of the impedance is 10Ω