A Circuit Problem

[shaidul]

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.

 

[jpanhalt]

Have you calculated the voltage across the capacitor before the switch changes? Maybe Figure 15.4 here will help: https://www.ece.umd.edu/class/enee206.S2004/lectures/lecture11.html

John

 

[ericgibbs]

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

 

[shaidul]

Thank you ericgibbs for that pdf file.But if you dont mind,can you also provide me with the solution to this problem.

 

[Ratchit]

Thank you ericgibbs for that pdf file.But if you dont mind,can you also provide me with the solution to this problem.

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

Ratch

 

[shaidul]

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

 

[Ratchit]

Yes the first one is the part a and b answers and the second is part c
View attachment 95630 View attachment 95631

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

 

[shaidul]

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

 

[Heidi]

** 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.

 

[Ratchit]

** 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:
View attachment 95650

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.

Did you read post #7 of this thread?

Ratch

 

[shaidul]

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

 

[Ratchit]

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

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

Ratch

 

[Heidi]

Did you read post #7 of this thread?

Ratch

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.

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

Maybe you would like to show us your own calculations?

 

[shaidul]

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

Ratch

no i couldnt understand.please re explain.

 

[Ratchit]

no i couldnt understand.please re explain.

What particular thing could you not understand?

Ratch

 

[DerStrom8]

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.

If the OP doesn't stop asking for answers, this thread will be closed.

 

[Ratchit]

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.

If the OP doesn't stop asking for answers, this thread will be closed.

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

Ratch

 

[Heidi]

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

 

[Ratchit]

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

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

Ratch

 

[DerStrom8]

Ratchit The numbers are reordered if a post is removed.

Heidi Done!