# 2 Port Networks - Impedance Parameters

1. Aug 30, 2012

### p75213

1. The problem statement, all variables and given/known data
see attached

2. Relevant equations

3. The attempt at a solution
\eqalign{ & {V_1} = {Z_{11}}{I_1} + {Z_{12}}{I_2} \cr & {V_2} = {Z_{22}}{I_2} + {Z_{21}}{I_1} \cr & {\rm{ - - - - - - - - - - - - - - - - - - - - - - - - - - - }} \cr & 2\angle 30 = 8{I_1} - j4{I_2} \cr & 0 = - j4{I_1} + 8{I_2} & \to {I_1} = {{8{I_2}} \over {j4}} = - j2{I_2} \cr & 2\angle 30 = - j16{I_2} - j4{I_2} \cr & {{2\angle 30} \over {20\angle - 90}} = {I_2} \cr & {I_2} = 0.1\angle 120{\rm{ A}} \cr}

As I2 is incorrect I haven't bothered with I1. Can somebody point out where the error is?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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2. Aug 30, 2012

### Staff: Mentor

[strike]Z11 is 6 ohms. EDIT: Oops, I failed to notice you'd included the 2 ohms there.[/strike]

Where it says 2∠30°, change it to 20∠30°.

Last edited: Aug 30, 2012
3. Aug 31, 2012

### rude man

Check the relation between I1 and I2. There's a sign error there!

Plus the magnitudes are wrong anyway unless you change the input to 20V or reduce the answers by a factor of 10 ...

Plus, the angle of I1 is off by 10 deg.

Not a good day for the quizmaster.

Last edited: Aug 31, 2012
4. Sep 1, 2012

### p75213

Thanks guys.

I have learned a lot from this book in spite of the many errors.