Question

In the circuit shown below, find the thevenin’s voltage across ‘ab’ terminals.

(a) 48.5∠40.35⁰

(b) 48.5∠-40.35⁰

(c) 49.5∠-40.35⁰

(d) 49.5∠40.35⁰

The question was asked during an internship interview.

I'm obligated to ask this question of Thevenin’s Theorem in section Steady State AC Analysis of Network Theory

Answer 1

Right option is (d) 49.5∠40.35⁰

For explanation: Though the thevenin’s equivalent circuit is not same as its original circuit, the output current and voltage are the same in both cases. The thevenin’s voltage is equal to the voltage across (4+j6)Ω impedance. VTh =50∠0^o×(4+j6)/((4+j6)+(3-j4))=49.5∠40.35⁰V.