# Write Differential Eq ?

1. Jun 25, 2012

Hi ,
Can anyone help me on this problem please?!
Answer is given but i want to know steps to come to it, i think i tried a lot to solve it but i couldnt come to the given result.
Thanks to all

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2. Jun 26, 2012

### tiny-tim

hi xmenus! welcome to pf!

show us what you've tried, and where you're stuck, and then we'll know how to help!

3. Jun 26, 2012

Here's the link of doc..I think i tried loop method and many other forms but.... here i just showed the analogy i tried but i couldnt come to the result.(First circuit is different one)
I took an other example just to show or ask if the other circuit can be solved with the same analogy?!

https://www.dropbox.com/sh/7g4vmpl4uhjbyl4/wwNdGrKm5o

Last edited: Jun 26, 2012
4. Jun 26, 2012

### tiny-tim

it's rather difficult to read

anyway, what is D ?

5. Jun 26, 2012

### psparky

That's a tough circuit you posted for finding a differential equation.

Don't know for sure....but perhaps a node analysis on the upper right hand node? Current in equal current out sorta thing.

Using SL and 1/(SC) may simplify things as well.

6. Jun 26, 2012

7. Jun 26, 2012

### tiny-tim

ah, D = d/dt !

ok, you've replaced C and R3 (in series) by an impedance Z1

(btw, wouldn't Z3 be an easier name to keep track of? )

then you've replaced R2 and Z1 (in parallel) by Ze

but then you've stopped (presumably you're going to replace L and Ze, then replace that and R1?)

well, that looks fine so far

what's the difficulty?​

8. Jun 26, 2012

The problem is that it's not working like that.I cant come to the result, i dont know!?

9. Jun 26, 2012

### tiny-tim

but you stopped, you only got as far as Ze

10. Jun 26, 2012

No,actually i worked on it till to the end but the result i got is not like the given one.
You are right, i didnt post other steps,but on that way it didnt work!

11. Jun 26, 2012

### tiny-tim

we can't comment on why it didn't work unless you show us what you did

12. Jun 26, 2012

Finally,after many attempts, i solved it :D !

I might post the solution so anyone can find it useful maybe.
Thank you a lot anyway,and thank for your time!

Last edited: Jun 26, 2012
13. Jun 26, 2012

Solution is in .pdf file.

Regards

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