# complex conjugate ??

Discussion in 'Homework Help' started by marty4, Sep 6, 2012.

1. ### marty4 Thread Starter New Member

Aug 27, 2012
3
0
Hi Guys,

I have a question thats bugging me, if you can help.

I need to calculate Is when I1 = 4 + j10 Z1= 9+J10 Z2=2 + j6.

Is= I1x Z1/Z1 + Z2.

Is this just multiplying by the complex conjugate?

Would I just do (9 +j10)
(9 +j10 + 2 + j6)

= (9 +j10) x (11 - j16)
(11 +j16) (11 - j16

Then multiply the answer by I1 which would be 4?

Thanks Guys.

2. ### nobody0608 New Member

Aug 4, 2012
28
2
Hello,

Let me check first whether I get what you means. Is the equation below same with yours?

If yes then your steps are correct, but the final answer is not equal to 4.

3. ### marty4 Thread Starter New Member

Aug 27, 2012
3
0
Hi,

Yes I meant, do the( Z1/Z1 + Z2 ) equation first then multiply by I1 (4)?

Cheers.

4. ### marty4 Thread Starter New Member

Aug 27, 2012
3
0
It's ok I got it..

Cheers....

5. ### WBahn Moderator

Mar 31, 2012
18,088
4,917
This equation has units problems. Z1/Z1 is simply 1 (no units), so (Z1/Z1 + Z2) is (1 + Z2) and you can't add something that has no units to something that has units of impedance (i.e., ohms).

Normally, if you have a Z1 and then talk about I1, it means that I1 is the current through Z1. But if I use that convention, then I have no idea what you are trying to do.

It would really, really help if you provided a circuit, or at least a description of a circuit, so that we didn't have to try to read your mind.