# A Circuit Problem

Discussion in 'Homework Help' started by shaidul, Nov 27, 2015.

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1. ### shaidulNew Member

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Hello,

Can anyone please solve the problem in the screenshot? This is a question from the book Electric circuits(9th edition) by James W nilsson and Susan Riedel.

Thank You.

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2. ### jpanhaltWell-Known MemberMost Helpful Member

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3. ### ericgibbsWell-Known MemberMost Helpful Member

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hi shaidul,
As you are studying s domain circuits you may find this PDF helpful.
E

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Thank you

6. ### RatchitWell-Known Member

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What is your solution? Post it first and we will look it over.

Ratch

7. ### shaidulNew Member

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Yes the first one is the part a and b answers and the second is part c

8. ### RatchitWell-Known Member

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OK, the solution is derived below. Ask if you have any questions. I expected the voltage to oscillate as the energy from the capacitor and the coil transferred energy back and forth, but it appears that 5000 ohms of resistance is enough to dampen any oscillations. You can see the oscillations if you lower the resistance to 2000 ohms.

Ratch

9. ### shaidulNew Member

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Please make sure you show all the steps of each part and mark them also with their part number.

10. ### HeidiMember

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** I'm a student.

First I'd like to show why we construct the s-domain circuit like that in the second diagram in post #6:

We can treat the first constant term as a voltage source, the second the voltage drop across the capacitor, the third across the resistor and the fourth across the inductor, so the equation itself indicates a kind of Kirchhoff's voltage law, and we build the s-domain circuit from it.

Next we can solve for I from the last equation in terms of s and the capacitor's initial voltage, then Vo is simply equal to IsL.

Once we have Vo in the s-domain, we can change it back to the corresponding time domain solution by reverse Laplace transform.

Hope it helps.

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Ratch

12. ### shaidulNew Member

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For post#9, i couldnt understand properly,please explain by solving the problem. Thanks

13. ### RatchitWell-Known Member

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The solution was given to you in post #7. What is there in post #7 you do not understand?

Ratch

14. ### HeidiMember

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Yes, I did. I was just trying to provide a possible reason why we draw a s-domain circuit like those procedures listed on a textbook. By solving the Laplace current in the last equation in post #9, I got the same transient voltage as yours.
Maybe you would like to show us your own calculations?

15. ### shaidulNew Member

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no i couldnt understand.please re explain.

16. ### RatchitWell-Known Member

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What particular thing could you not understand?

Ratch

17. ### DerStrom8Super ModeratorMost Helpful Member

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shaidul DO NOT ask for the members to give you answers. This is YOUR homework, not theirs. YOU need to learn HOW to solve it, not just ask for answers. That defeats the purpose of this forum.

Everyone else, please do not give answers to the problem. By doing so you are not helping the OP. You may point him in the right direction, but HE must do all of the work.

18. ### RatchitWell-Known Member

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Strange. He already has the answer from post #7, and he still does not get it.

Ratch

19. ### HeidiMember

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Sorry, can I ask DerStrom8 to delete my last post?
Post #16 must appear during my "solving" the problem and uploading it ..., Sorry!

20. ### RatchitWell-Known Member

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Posts appear in sequential numerical order. Why would you want to delete your post? It appears to contain correct information.

Ratch

21. ### DerStrom8Super ModeratorMost Helpful Member

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Ratchit The numbers are reordered if a post is removed.

Heidi Done!