# Help on RC circuit for laplace!

Discussion in 'Homework Help' started by kling, Jun 27, 2012.

1. ### kling Thread Starter New Member

May 12, 2012
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help me solved qn 2 and 3!!!!

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2. ### t_n_k AAC Fanatic!

Mar 6, 2009
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As they say - "Don't feed the trolls"

3. ### WBahn Moderator

Mar 31, 2012
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I'm not at all sure that we are dealing with a troll. I think there are a number of students taking this class that, through the grapevine, have learned about the forum. I don't know that they are aware that others in their class have been asking the exact same problem. At least this time it wasn't asked using the exact same screenshot!

Kling: Look at the other recent threads in the Homework Help section and you will find a couple dealing with this problem. If you have questions that aren't answered there, please reply to one of those threads instead of propogating this new one.

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
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I've grown so "fond" of this question I think I'll post it myself.

5. ### WBahn Moderator

Mar 31, 2012
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When you do, be sure to correct the "hint". I find "hints" with errors are pretty poor hints.

6. ### kling Thread Starter New Member

May 12, 2012
12
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I still can't get the equation that we have to prove...

Mar 6, 2009
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8. ### WBahn Moderator

Mar 31, 2012
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We are not mind readers. Show us what you have done so far so that we can see where you are going astray.

9. ### kling Thread Starter New Member

May 12, 2012
12
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Cos the qn is a bit different from the others. The Vout=Vr, we can't get the equation for Vc.

10. ### WBahn Moderator

Mar 31, 2012
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It sure looks like the same question. How is it different?

Why not? And why do you think that Vout=Vr, given the discussion on this point that has taken place in the other threads?

Are we to conclude that your position is that you should be expected to show any effort or any work and we are to just solve the problem for you and give you the solution all ready to copy and turn in as your own work?

Well, that's not what this forum is about. So I (and I suspect many others) have no interest in helping you until you show some indication that you have made a good faith effort to work the problem yourself.

11. ### kling Thread Starter New Member

May 12, 2012
12
0
I solved qn2 alr. Can help me on q3? I don't understand what is transient state and steady-state voltages..

12. ### t_n_k AAC Fanatic!

Mar 6, 2009
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Anything that is transient fades with the passing of time - like human physical beauty.

Things in steady-state continue on unchanged from the past to the present and into the future in a systematic / predictable manner - like ....????

Which of the voltages fade with the passing of time - why?

Which voltages continue on with the passing of time in a unchanging systematic / predictable manner - why?

13. ### kling Thread Starter New Member

May 12, 2012
12
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so transient state voltages fade with the passing of time, because its a undesire voltage?

And steady-state voltage continue on with the passing of time in a unchanging systematic / predictable manner. but i dont know why...

14. ### WBahn Moderator

Mar 31, 2012
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It has nothing to do with what's desireable and what's not. When you ring a bell, the desired response is that it wiggle and make a pretty sound for a while and then go silent. That's a transient response. When you turn on an oscillator, the desired response is that it output a nice steady tone until it is turned off. That's a steady state response. it will do some funky things for a little bit when you first turn it on and finally settle down. The funky stuff is the transient response.

If you drop a heavy box onto a diving board, it will bounce up and down for a while and eventually settle to a position that is lower than it would be if the diving board had been a rigid steel beam. The wiggling that dies out is the transient response and the final displaced position is the steady state response. Which of those, if either, is "desired" depends on what the point was in choosing to set a heavy box on a diving board. The system is what the system is and it doesn't give a damn about what is and what isn't "desired".

15. ### kling Thread Starter New Member

May 12, 2012
12
0
oh okay. how about qn 4, i know is a high pass filter. but how do i explain.

16. ### WBahn Moderator

Mar 31, 2012
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Q1) How do you know it is a high pass filter?

Q2) What IS a high pass filter?

Q3) What should the amplitude of the steady state response (for a given amplitude input signal) high pass filter look like at high frequencies? At low frequencies?

Q4) What is a low pass filter?

Q5) What should the amplitude of the steady state response (for a given amplitude input signal) of a low pass filter look like at high frequencies? At low frequencies?

Q6) What does the amplitude of the steady state response (for a given amplitude input signal) of THIS filter look like at high frequencies? At low frequencies?

Q7) Based on the answers to Q3, Q5, and Q6, what kind of filter is this?