Solve RC Integrator Circuit Problem | Romania Student

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    Circuit Rc
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Discussion Overview

The discussion revolves around solving an RC integrator circuit problem, specifically focusing on determining the input voltage V1 and calculating the output voltage V2. Participants explore the implications of given circuit parameters, including capacitance, resistance, and frequency, while addressing the lack of a complete problem statement.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • A participant expresses uncertainty about how to choose V1, proposing V1 as cos(wt) with w defined as 2π times the frequency (10 kHz).
  • Several participants note the absence of a complete problem statement, questioning what is specifically being asked regarding V2.
  • One participant suggests that V2 can be derived from the integral of V1, indicating a possible relationship between the two voltages.
  • Another participant confirms that the choice of V1 as cos(wt) is acceptable under the condition that R is much greater than 1/(ωC), prompting further exploration of this condition.
  • Participants discuss the approximation used in the relationship between current and voltage, highlighting the omission of small impedance from the capacitor.
  • There is a suggestion to consider solving the problem in the frequency domain, questioning whether this approach has been covered in class.
  • A participant attempts to calculate the maximum value of V2 based on their understanding of sine functions, but another participant indicates that the calculation may not be correct and encourages working out the correct expression first.

Areas of Agreement / Disagreement

Participants generally agree on the need for a complete problem statement and the validity of using V1 as cos(wt) under certain conditions. However, there is no consensus on the correct approach to calculating V2 or the appropriateness of the approximations used.

Contextual Notes

The discussion highlights limitations in the provided information, particularly the incomplete problem statement and the assumptions regarding circuit parameters. The implications of approximations and the choice of analysis method (time domain vs. frequency domain) remain unresolved.

hmzi123
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Homework Statement
RC integrator circuit
Relevant Equations
RC integrator circuits
1.png

Hello, i am student from Romania ( first year) and my physics teacher told us to solve this problem. We know that C=150 nanofarad, R= 1000 ohms, and the frequency we should take is more then 1061 ( 10kHz, to be more exactly). My problem is that i don't know what to take as V1 ( i took it coswt, where w=2*pi*10000), can you help me understand how to choose the V1, and what its formula is so that I can calculate and find V2.
 
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Hello hm, :welcome: !

hmzi123 said:
told us to solve this problem
Did you forget to mention the 'problem'? I don't see what is asked !
 
BvU said:
Hello hm, :welcome: !

Did you forget to mention the 'problem'? I don't see what is asked !
The value of V2. Sorry!
 
No need to apologize. Can you render the complete problem statement ? Asking for V2 when nothing is given for V1 is weird. The picture does not help much either. The only thing I can suppose is that you are asked to derive ##V_2\; {\bf \approx}\; \displaystyle {1\over RC}\int V_1 dt\quad ## i.e. show what is small enough to be ignored wrt what else.
 
BvU said:
No need to apologize. Can you render the complete problem statement ? Asking for V2 when nothing is given for V1 is weird. The picture does not help much either. The only thing I can suppose is that you are asked to derive ##V_2\; {\bf \approx}\; \displaystyle {1\over RC}\int V_1 dt\quad ## i.e. show what is small enough to be ignored wrt what else.
I took v1 as coswt where w is the 2*pi*frequency ( in this case the teacher said to pick the frequency 10000). Is this correct as a formula for v1 or not?
 
It satisfies ##R >> {1\over \omega C}##, so yes.

[edit] actually more ##R > {1\over \omega C}## but you can calculate that for yourself, can't you.

Can you find out why it says ##\ \approx\ ## and not ##\ =\ ## ?
 
BvU said:
Can you find out why it says ##\ \approx\ ## and not ##\ =\ ## ?
It should be ##\approx## there and the line above it (if I'm seeing that tiny font correct) because ##i \neq V_1/R##. They're omitting the small impedance from the capacitor, which is being dominated by a much larger ##R##.

Another question is why not solve this in frequency domain? Has that been covered in the class?
 
1.jpg

After solving this is what i got. I know i should calculate v2 max value so where i wrote sin(2pi*10000t) i thought that the max value of any sin is 1 so that means the fraction will be 1/(2*pi*10000). Did i solve this any good?
 
Joshy said:
It should be ##\approx## there and the line above it (if I'm seeing that tiny font correct) because ##i \neq V_1/R##
Correct, but you are giving away the "why" -- and that is what I think the exercise wants Hm to find out.
hmzi123 said:
After solving

1590743731166.png

No, not exactly. Work out the correct expression and then apply the approximation.
 

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