How to graph amplitude vs. frequency for a Low-Pass Filter?

Click For Summary

Homework Help Overview

The discussion revolves around graphing the theoretical amplitude of the output from a low-pass filter against frequency, specifically in the context of an RC circuit. The original poster is seeking clarification on the appropriate equations to use and the meaning of certain variables in their notes.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to relate resistance and capacitance to produce a graph but is uncertain about the variable epsilon in their equation. Some participants question the correctness of the equations used and the implications of plotting in the wrong frequency range.

Discussion Status

Participants are actively discussing the definitions and relationships between variables, with some providing guidance on terminology and potential misunderstandings. There is an acknowledgment of confusion regarding the equations and their application in the context of the problem.

Contextual Notes

There is a noted lack of clarity regarding the variable epsilon and its relation to capacitance, as well as confusion about the correct expression for capacitive reactance. The original poster's attempts to graph the output amplitude have led to unexpected results, indicating possible issues with the frequency range used.

eroc1002
Messages
1
Reaction score
0

Homework Statement


For my lab class my professor wants us to graph the theoretical amplitude of the output from a low-pass filter vs. frequency. I have the resistance and capacitance that I chose for the RC circuit and a V(in). Is there an equation that I should be able to use to relate these and produce a graph?

Homework Equations


In my notes I have an equation Vout = Vin*(Rc/sqrt(R^2 + Rc^2) and Rc = 2πfε but I have no idea what epsilon represents because I forgot to ask my professor when I was taking the notes.

3. Attempt at a solution
After doing some research, I tried to use 1/sqrt(1+(2πfRC)^2)to get a ratio of Vo/Vin but all I got was a straight line.
 
Physics news on Phys.org
I think the epsilon should be C and RC is the capacitive reactance 2πfC.

As to why you got a straight line, it probably has to do with not plotting in the correct frequency range.
 
eroc1002 said:
In my notes I have an equation Vout = Vin*(Rc/sqrt(R^2 + Rc^2) and Rc = 2πfε
First, don't use "Rc" for capacitive reactance. Use Xc. "R" is always resistance in this context.
Second, capacitive reactance is not 2πfC. It's the inverse.
 
rude man said:
... capacitive reactance is not 2πfC. It's the inverse.
Right you are. I missed that. :oops:
 

Similar threads

Combining High and Low Pass Filters
  • · Replies 2 ·
Replies
2
Views
2K
Bandpass Filter Homework Statement
  • · Replies 6 ·
Replies
6
Views
2K
Why can we add impedances in series?
  • · Replies 4 ·
Replies
4
Views
2K
High School RC Low Pass Circuit Sine Wave Response
  • · Replies 7 ·
Replies
7
Views
3K
How do I determine the resistance for RLC low pass filter?
  • · Replies 4 ·
Replies
4
Views
1K
High School Multiple frequency EMFs and capacitors
  • · Replies 9 ·
Replies
9
Views
1K
LT spice result analysis, Capacitance Multiplier vs RC filter circuit
  • · Replies 2 ·
Replies
2
Views
2K
AC Power RC series circuit low pass filter, find frequency given gain.
  • · Replies 1 ·
Replies
1
Views
5K
Capacitor Voltage Equations: Explained
  • · Replies 4 ·
Replies
4
Views
2K
Trouble with a Passive RC Twin-T Notch Filter
  • · Replies 2 ·
Replies
2
Views
5K