Practical: Graph need to pass through orgin?

  • Context: High School 
  • Thread starter Thread starter dove
  • Start date Start date
  • Tags Tags
    Graph Practical
Click For Summary

Discussion Overview

The discussion revolves around the necessity of graphs passing through the origin in physics practicals, particularly in the context of drawing graphs for experiments involving resistance, current, and other variables. Participants explore different scenarios and conditions under which graphs may or may not pass through the origin.

Discussion Character

  • Homework-related
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant questions whether all graphs in physics experiments must pass through the origin, citing Ohm's law as a specific case where this is true for resistance.
  • Another participant states that whether a graph passes through the origin depends on the function being graphed, specifically if f(0) equals zero.
  • A different participant mentions a concept of "zero error" related to measurements that do not pass through zero, suggesting that this could indicate improper calibration of measuring instruments.
  • One participant argues that if a graph does not pass through the origin, it may indicate a need for calibration of the measuring devices used in the experiment.
  • Another participant raises a scenario where a graph plotted from experimental data does not pass through the origin, questioning if this is acceptable when the axes are not related by a linear equation.
  • A participant shares their experience of misunderstanding the requirements for a graph in their practical exam, expressing concern about potential mark deductions for not following instructions.
  • Responses to the participant's concern include skepticism about the validity of their graph due to not adhering to the assignment's requirements.

Areas of Agreement / Disagreement

Participants express differing views on whether graphs must pass through the origin, with some asserting it is necessary under certain conditions while others suggest it depends on the specific relationship between the variables being graphed. The discussion remains unresolved regarding the general rule for all physics graphs.

Contextual Notes

Participants reference specific cases, such as Ohm's law and the concept of zero error, but do not reach a consensus on the broader applicability of these ideas to all physics experiments. There is also mention of potential errors in measurement and the implications for graphing.

dove
Messages
4
Reaction score
0
Hi there, I need immediate help as my pratical exam is on next Monday [18/10/04] and I would greatly appricate if anyone can help me with my doubts.

We all know that for physics practical, mostly likely we have to draw a graph to conclue our results. However, after ploting the correct points, I always wonder if you have to past through the orgin, O. My teacher says that if we are finding the resistance, then if passes through O because it obeys the Ohm's law. However, what are about others? like current? Do we also have to pass through O.

I would just like to confrim with you if am I correct to say that in Physics experiment, we always draw a best fit line in all experiments expect cooling curve. If I'm wrong, please tell me.

-Thanks in advance-
 
Physics news on Phys.org
That depends completely on the function f you're talking about!
If f(0)=0, then the graph DOES go through the origin, if f(0) is not equal to 0, then your graph does NOT go through the origin.
 
Well, when we did the electricity and magnetism bit of the AS syllabus my teacher said that if the graph didn't go through zero it was called a zero error, and it just meant that the ammeter/voltmeter wasn't set properly or something. Not sure if that helps you though! Sorry!

Ooo, also, isn't current proportional to voltage? So, the graph should also pass through zero? Again, not sure if I'm right!
 
Last edited:
That kind of error is verry common and its very easy to solve. If you see Ohm's law V = IR and you plot it, you get a line which passes through origin. If not, then the voltage is not correctly measured. Think that voltage is a potential, so we measure variations but not absolute values. So, if you can get the line pass through the origin, you have to calibrate the voltimeter measuring the voltage of ground and that value will be your zero, so the next values you take have an error by excess, and to get the exact value you have to rest your zero to all of your experimental points of voltage. Then, if you plot it you will get a line which passes trough the origin.

MiGUi
 
Okay, what if the graph is plotted without a formula connected together? For example, in the picture below, they ask we to plot (h1-h3) agasint (h2-h3)? I did that experiment before, it didn't get to past through the orgin. So, does that mean that only if the y-axis and x-axis are related by a straight line equation (y=mx+c), for exmaple, V=RI, Q=IT & V=W/Q, then it is a best fit graph which passes through the orgin?
 

Attachments

  • pic1.jpg
    pic1.jpg
    11.3 KB · Views: 1,205
Thanks for all your help. I had my physics pratical today. I made a huge, unforgiveable mistake. They didn't ask us to draw a striaght line graph, but a curve. I missed this piece of information a drew a straight line graph without passing through the orgin. The total marks for the graph is 4. I did label the axes, give the title of the graph as well as the scale. So, how much do you people think the cambridge markers will deduct because I never follow the instruction? Will they take away all the 4 full marks? :cry:
 
Very probably; since your answer makes no sense.
 
Oh no.. then I'm very, very dead... :frown: :cry:
 

Similar threads

High School Occam's razor in science: all-time practice or modern fashion?
  • · Replies 63 ·
3
Replies
63
Views
5K
High School You normally go through B and C when passing from A to D
  • · Replies 20 ·
Replies
20
Views
3K
High School Graphing trip efficiency - distance over time
  • · Replies 14 ·
Replies
14
Views
3K
High School What sound frequencies can pass through a hole in a wall?
  • · Replies 31 ·
2
Replies
31
Views
5K
High School Learn Special Relativity: Understanding Graphs for X-T System
  • · Replies 13 ·
Replies
13
Views
2K
High School Understanding Flux: The Measure of Field Lines Passing Through a Surface
  • · Replies 35 ·
2
Replies
35
Views
5K
High School Why do photon polarization experiments show similar outcomes in different situations?
  • · Replies 11 ·
Replies
11
Views
3K
The integral of a function ##f(x)## from its graph
  • · Replies 15 ·
Replies
15
Views
2K
High School Probability of a photon passing through a filter
  • · Replies 5 ·
Replies
5
Views
2K
High School Does the CMB give us absolute space and time in practice?
  • · Replies 70 ·
3
Replies
70
Views
8K