Question

In the circuit given below, the maximum power absorbed by the load resistance RL is ___________

(a) 2200 W

(b) 1250 W

(c) 1000 W

(d) 621 W

I got this question during an interview for a job.

The above asked question is from Advanced Problems on Reciprocity Theorem in portion Useful Theorems in Circuit Analysis of Network Theory

Answer 1

The correct choice is (d) 621 W

To explain: RL = \(\sqrt{R_{TH}^2+X_{TH}^2}\)

= \(\sqrt{3^2+4^2}\) = 5

Now, 110 = (6 + j8 + 5) I1 + 5I2

And 90 = (6 + j8 + 5) I2 = 5I1

∴ I1 = 5.5 – 2.75j and I2 = 4.5 – 2.2j

Total current in RL = I1 + I2 = (10 – 4.95j) A = 11.15 A

∴ Power absorbed by RL = I^2R

= 11.15^2 × 5 = 621 W.