Graphing Resistance vs. Bandwidth, why wouldn't go throught the origin?

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Homework Help Overview

The discussion revolves around the relationship between resistance and bandwidth, specifically why the graph of resistance versus bandwidth does not pass through the origin. The original poster expresses confusion regarding their findings from a LINEST function analysis in Excel, which indicates a y-intercept at approximately 288 Hz.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand the implications of their data and the behavior of the graph. Some participants suggest potential reasons for the observed y-intercept and question the nature of the measurements being taken. Others raise the possibility that the measuring instruments may influence the results.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the data and its implications. Some guidance has been offered regarding the potential effects of measurement tools, but no consensus has been reached regarding the underlying reasons for the graph's behavior.

Contextual Notes

Participants note the lack of detailed information about the experimental setup and the specific system being measured, which may be relevant to understanding the results. The original poster's manual suggests that the relationship should not allow both variables to be zero simultaneously, adding to the complexity of the discussion.

crh
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I am using Excel and plotting a line of best fit for Resistance vs. Bandwidth. I used the LINEST function to get my values, and it shows that it would cross the y-intercept at around 288 Hz. I am just wondering why when using resistance vs bandwidth it would never cross at the origin. That is what my manual says, and I guess that I am just confused as to why they could both never be zero at the same time. Am I over thinking this, could someone just clarify it for me.
 
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Two possible reasons come to mind:

1. The scatter in the data produces a best-fit line that is close to, but not through, the origin.

2. The data consists of points relatively close to each other, but far away from the origin. So a small amount of scatter in the data produces a best-fit line that is not even close to passing through the origin.

Without seeing your data, it's impossible to give a definitive answer. You haven't told us any details about the system or circuit being measured. If the bandwidth data are in the MHz range, then 288 Hz is for all practical purposes at the origin.
 
R(x) BW(y)
50 457
100 636
200 937
300 1296
400 1614
500 1938
600 2290
800 2925
1000 3630

LINEST function:
3.322306649 288.8765265
0.016948199 9.025789158
0.999817868 15.33684586
38426.63043 7
9038667.468 1646.531886

This is my data. I know that as resistance increases, bandwidth increases. I get the relationship between the two. I just don't understand that no matter what, when I graph them that it would never go through the origin. My manual says that no matter the numbers it would never be y=0, x=0. I guess I just can't understand why.
 
Last edited:
I plotted your numbers in Excel, and you're right it clearly does not go through the origin. There is very little scatter in the data and it produces a nice straight line.

I don't know anything about what you're actually measuring, but it might be that your measuring instruments contribute to the bandwidth. If so, then even when resistance=0 there will be a measureable bandwidth due to the instrumentation.

Realize that I am merely guessing, since you haven't described your experimental setup.
 

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