# What Am I Doing Wrong?

Discussion in 'Homework Help' started by bembe 24, Aug 10, 2016.

1. ### bembe 24 Thread Starter New Member

Aug 10, 2016
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My solution:

Is answer correct? can someone verify my solution... thanks )

2. ### Jony130 AAC Fanatic!

Feb 17, 2009
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For me solution looks good, but you could write them differently.

Aug 10, 2016
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4. ### DGElder Member

Apr 3, 2016
310
72
C1 + C2 = 1/(1/C1 + 1/C2)

and where does it say C1=C2=C?

5. ### bembe 24 Thread Starter New Member

Aug 10, 2016
10
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so does that make the final answer

Ls/(Cs/2 +Ls) ??

6. ### bembe 24 Thread Starter New Member

Aug 10, 2016
10
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can i really neglect R in the circuit?

7. ### bembe 24 Thread Starter New Member

Aug 10, 2016
10
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correct me if i am wrong. If I neglect R in the circuit then C1, L and C2 are in series right?

8. ### DGElder Member

Apr 3, 2016
310
72

That is not even a solution because C is undefined.

9. ### DGElder Member

Apr 3, 2016
310
72
They are in series whether you neglect R or not.
The answer is not dependent on R.

10. ### bembe 24 Thread Starter New Member

Aug 10, 2016
10
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im sorry my bad. not solution but an equation

11. ### bembe 24 Thread Starter New Member

Aug 10, 2016
10
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so if C1, L and C2 are in parrallel, then rewrite the equation with respect to the impedance then does this make

1/Cs + Ls + 1/Cs right?

12. ### DGElder Member

Apr 3, 2016
310
72
Where in that circuit is there a component called C? There is none.

13. ### DGElder Member

Apr 3, 2016
310
72
Is it possible you think the s in Cs stands for series?

14. ### bembe 24 Thread Starter New Member

Aug 10, 2016
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its a transfer function. from time domain to s-domain. that is what s means

15. ### DGElder Member

Apr 3, 2016
310
72
It is a complex number used as the frequency parameter in Laplace transforms. I am glad you know it does not stand for series. So moving on....

What is the solution to your circuit?

AND.

If:
R = 2000 ohms
C1 = 3 F
C2 = 6 F
L = 5 H

What is the transfer function?

Last edited: Aug 10, 2016
16. ### bembe 24 Thread Starter New Member

Aug 10, 2016
10
0
there were no given values of each component. What you see is what you get . Its just a constant variable.
TF = 5/90s^2 + 9
is it correct??

17. ### DGElder Member

Apr 3, 2016
310
72
It is not correct. I can't help you if you don't show me each step of how you got to your solution.

Just giving you the answer will teach you nothing.

18. ### WBahn Moderator

Mar 31, 2012
17,457
4,701
As has already been noted, you can't just assume that C1 and C2 have the same value. So your solution must reflect this reality.

Also, you need to pay attention to order of operations.

1/Cs is equivalent to (1/C)s which is equivalent to s/C.

19. ### bembe 24 Thread Starter New Member

Aug 10, 2016
10
0

sorry low quality cam
i followed all your instructions. Is this correct?

20. ### DGElder Member

Apr 3, 2016
310
72
"Sorry" doesn't make it any more visible.

If it says what I think it says it is not correct. The setup is correct but your algebra is wrong somewhere and since, once again despite requests, you show none of your steps I can't help you. Maybe you have no steps and are just guessing. Either way I can't help you.

Also, I think your notation is misleading if not incorrect. It looks like you are subscripting s: s1, s2. There is only one s. Subscript the capacitors: C1,C2. Where applicable, putting s in front of C would make it more legible.

Last edited: Aug 10, 2016