Question

For the circuit given below, the value of g11 and g21 are _________________

(a) g11 = 0.0667 – j0.0333 Ω, g21 =  0.8 + j0.4 Ω

(b) g11 = -0.0667 – j0.0333 Ω, g21 = -0.8 – j0.4 Ω

(c) g11 = 0.0667 + j0.0333 Ω, g21 = 0.8 + j0.4 Ω

(d) g11 = -0.0667 + j0.0333 Ω, g21 = 0.8 – j0.4 Ω

I had been asked this question during an online interview.

This intriguing question comes from Advanced Problems Involving Parameters topic in portion Two-Port Networks of Network Theory

Answer 1

Right option is (c) g11 = 0.0667 + j0.0333 Ω, g21 = 0.8 + j0.4 Ω

For explanation I would say: V1 = (12-j6) I1

Or, g11 = \(\frac{I_1}{V_1} = \frac{1}{12-j6}\) = 0.0667 + j0.0333 Ω

g21 = \(\frac{V_2}{V_1}  = \frac{12I_1}{(12-j6) I_1}\)

= \(\frac{2}{2-j}\) = 0.8 + j0.4 Ω.