Question

In the circuit given below, the value of RL for maximum power transfer is ___________

(a) 2.4 Ω

(b) 2.6 Ω

(c) 2.8 Ω

(d) 3.0 Ω

This question was posed to me in an online quiz.

This intriguing question originated from Advanced Problems on Network Theorems in section Useful Theorems in Circuit Analysis of Network Theory

Answer 1

The correct option is (c) 2.8 Ω

Easiest explanation: Using Y-∆ transformation,

RAB = (9+9 || 6) || (9||6)

= (18 || 6) || (9 || 6)

=\(\left(\frac{18×6}{18+6}\right) || \left(\frac{9×6}{9+6}\right)\)

= 4.5 || 3.6

= \(\frac{4.5×3.6}{4.5+3.6}\) = 2.8 Ω.