Question

The values of z11 and z21 for a T circuit having resistances 20 Ω each is _____________

(a) 40, 20

(b) 40, 60

(c) 60, 40

(d) 40, 40

The question was asked in an online interview.

I need to ask this question from Laplace Transform of a Periodic Function in section Application of the Laplace Transform in Circuit Analysis of Network Theory

Answer 1

Right choice is (a) 40, 20

To explain: To determine the values of z11 and z21, we apply a voltage source V1 to the input port and leave the output port open.

Thus, z11 = \(\frac{V_1}{I_1}  = \frac{(20+20) I_1}{I_1}\)

= 40 Ω

Now, z21 is the input impedance at port 1.

So, z21 = \(\frac{V_2}{I_1}\)  = 20 Ω.