K I'll have a look at that when I get home. Is that value I have in post 9 correct?

No, I mean the \(\omega\) from your class whiteboard.
You'll need to do this:

\(\displaystyle{Z_{AB} = \frac{R}{1+\left ( R\omega C \right )^{2}} = \frac{R}{1+\left ( RC \right )^{2}\cdot \frac{R^{2}C-L}{R^{2}LC^{2}}} = \frac{R}{1+\frac{R^{2}C-L}{L}} =\frac{R}{\frac{L+R^{2}C-L}{L}} =\frac{RL}{R^{2}C} = \frac{L}{RC}}\)

 

Yes that' the ones exactly MrAI. This is an electronics module I'm studying. Now I must warn you I'm completely new to derivations and will probably ask what seem to be the most stupid questions ever, to start with. I have a weird ability to comprehend the complicated and be lost on the simple. But if you walk me through one or two, I'll probably be fine.

Hello again,

Well, did you ever do a simple circuit with a resistor in series with a capacitor and driven by a voltage source like a unit step?
I dont know exactly what you've done in the past so i have to ask.

 

Yes that' the ones exactly MrAI. This is an electronics module I'm studying. Now I must warn you I'm completely new to derivations and will probably ask what seem to be the most stupid questions ever, to start with. I have a weird ability to comprehend the complicated and be lost on the simple. But if you walk me through one or two, I'll probably be fine.

Here is a source free RL circuit.
Do you have any idea how to start solving this?

 

Here is a source free RL circuit.
Do you have any idea how to start solving this?

Hi MrAl,
I think you forgot to attach the picture of the RL circuit.

 

Hi MrAl,
I think you forgot to attach the picture of the RL circuit.

Hi,

Ha ha, yeah thank you, i'll put it here now. Sorry guys.

Kevin:
Here is a source free RL circuit (ground optional).
Do you have any idea how to start solving this?

 

Sorry guys for my delay... I managed to contract the nova virus and it wasn't pleasant... no siree...
Anyways I'l spare you the details... kk.

I'll have a go at this MrAI. I may require a bit of hand holding at first till I find my feet.
I've done unit step functions. Natural and forced responces... 1st and 2nd order... but we just assumed the equation. Then calculated the values for the circuit and tua. Drew the graph... Boom done.

Very cool Scorpion. Yeh!!! I've actually got a step further... Only took me a week... Lol and sigh...
Anyways nice... So there are 6 equations there after the ZAB =
See that 4th one...? This is going to sound like a stupid question but:- which L value from the 3rd equation is making the 1+ turn into an L? If you know what I mean?
Surely it' not the L in the denominater?
I've seen stuff like this before for example 4/4+3 = 1 + 4/3... But the logic of this is escaping me. Also it doesnt add up in my calculator when I assign it values. Though I could be inputting it incorrectly.

One more thing sorry... how are you making the forum display those math functions, is there a thread, on how to do it?

 

Sorry guys for my delay... I managed to contract the nova virus and it wasn't pleasant... no siree...
Anyways I'l spare you the details... kk.

I'll have a go at this MrAI. I may require a bit of hand holding at first till I find my feet.
I've done unit step functions. Natural and forced responces... 1st and 2nd order... but we just assumed the equation. Then calculated the values for the circuit and tua. Drew the graph... Boom done.

Very cool Scorpion. Yeh!!! I've actually got a step further... Only took me a week... Lol and sigh...
Anyways nice... So there are 6 equations there after the ZAB =
See that 4th one...? This is going to sound like a stupid question but:- which L value from the 3rd equation is making the 1+ turn into an L? If you know what I mean?
Surely it' not the L in the denominater?
I've seen stuff like this before for example 4/4+3 = 1 + 4/3... But the logic of this is escaping me. Also it doesnt add up in my calculator when I assign it values. Though I could be inputting it incorrectly.

One more thing sorry... how are you making the forum display those math functions, is there a thread, on how to do it?

Hi again,

I wasnt sure where to start because i dont know everything that you have done in the past.
For example, did you work with initial values yet or not?
Have you solved a lot of resistor only problems (possibly with a voltage source too)?

 

I could do a circuit with values. Convert it to complex terms and solve. No problems... its just these derivations. Heres what I've got so far. I don't want to get too far ahead as I'll probably be making a lot of mistakes and I 'd prefer the correction as I progress.

K now I'm watching a vid of how to do this but the teacher is using values. I'm trying to follow using the terms.

K so here it is.

 

I could do a circuit with values. Convert it to complex terms and solve. No problems... its just these derivations. Heres what I've got so far. I don't want to get too far ahead as I'll probably be making a lot of mistakes and I 'd prefer the correction as I progress.

K now I'm watching a vid of how to do this but the teacher is using values. I'm trying to follow using the terms.

K so here it is. View attachment 146644

Hi,

That may not be a bad start really, but where did 'i' go and where did v(t) go?
If you lose a variable you should say why, even if briefly.

Nice start though.
You can also use separation of variables on these.

If you would like to work with numbers first, make R=4 Ohms and L=2 Henries and I0=3 amps.

 

Thanks MrAI I'm not sure how useful this video is going to be. The terms start to become very convoluted while the teacher simplifies the values. Also she has chosen values for R L and V. Not the current.
Her values are:-
R = 10
L = 2
V = 40

Following on from that last photograph ^

I placed the equation, as she is explaining it, on the left hand side there.

The next step the equation becomes a tangled mess.
I've put the next step down below, first using the terms, then using the values.

This is the vid I'm using for your information:-

Here's my next step using the values she has:-

 

Sorry slight correction those terms should read

 

About the mathematical formulas in the forum:
https://forum.allaboutcircuits.com/...thematical-formula-editor.60409/#post-1094760

 

Sorry slight correction those terms should read

View attachment 146685

Hello,

Not sure why you would start a new circuit when you never did the old, easier circuit yet.
You also did not answer the questions i asked about where 'i' went.
If you cant answer a simple question like that and want to jump around from circuit to circuit, it wont help you at all.

 

Thanks Scorpion, for some reason google says it's blocking the page from displaying correctly. Must be something to do with my security settings. I'll have a look at it later. Thank you though Very much. I had planned to write out a thank you using the code ah well.

 

Hello,

Not sure why you would start a new circuit when you never did the old, easier circuit yet.
You also did not answer the questions i asked about where 'i' went.
If you cant answer a simple question like that and want to jump around from circuit to circuit, it wont help you at all.

Ok sorry MrAI. I suppose the experience will help. I will try your version here now. See if I can work through it myself. Apologies

 

Ok so I've got to this point here... now usually this is the point were we would introduce, this integrating factor. Though I'm not sure that' the way to go with this one.

 

Ok I tried to follow that method as close as possible here's what I get but I don't know if it' correct.

 

Hi KevinEamon,

What is V(t) there? Why did you include it in the equation?
Is R = 2 ohm and L = 2H?

Also do you know KVL?

 

Would it have been better if I called it E(t)?

 

Would it have been better if I called it E(t)?

The name is not important now but the circuit in that image has no V(t) or E(t) at all.
Do you know KVL? Let's try to apply KVL to that circuit and see what you would get.