Question

Find the current through (5+j4) Ω resistor.

(a) 0.9-j0.2 A

(b) 0.78-j0.1 A

(c) 2.7-j0.5 A

(d) 1A

This question was addressed to me at a job interview.

This interesting question is from Thevenin and Norton Equivalents,  More on Deriving a Thevenin Equivalent topic in portion Techniques of Circuit Analysis of Electric Circuits

Answer 1

Correct answer is (a) 0.9-j0.2 A

To elaborate: 1. Remove the 5+j4 Ω branch and calculate thevenin’s voltage.

                           (V= v across 6Ω resistor- v across 8Ω resistor)

                        2. Calculate Zth. (10//6 and 8//8)

                        3. Current= (Vth/ (Zth+Z).