Resistance as a Function of Temperature

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Discussion Overview

The discussion revolves around the relationship between resistance and temperature, particularly in the context of a lab experiment where unexpected results were observed. Participants explore the behavior of various components, including resistors, diodes, and inductors, and how their resistance changes with temperature. The conversation includes elements of experimental analysis and potential explanations for the observed data.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant notes that resistance in conductors typically increases with temperature, yet their data shows a decrease in resistance for resistors, diodes, and copper wire.
  • Another participant suggests that the behavior of resistors may depend on their construction, indicating that some resistors could have a negative temperature coefficient.
  • A participant mentions that diodes do not exhibit linear resistance and references their current-voltage characteristics, which could complicate the interpretation of resistance changes.
  • There is speculation that the observed negative temperature coefficient in the copper wire and resistors could be due to manufacturing variations or the nature of the components used.
  • Concerns are raised about the possibility of improper use of equipment or equipment malfunction affecting the results.
  • A later reply emphasizes the need for more details about the experimental setup to provide better assistance.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the reasons for the unexpected results, with no consensus on whether the findings are due to the components' characteristics, experimental error, or equipment issues. Multiple competing views remain regarding the interpretation of the data.

Contextual Notes

Limitations include a lack of detailed information about the experimental setup and the specific types of components used, which may affect the interpretation of the results. The discussion does not resolve the underlying reasons for the observed resistance behavior.

Who May Find This Useful

This discussion may be of interest to students and practitioners involved in experimental physics or electrical engineering, particularly those studying the effects of temperature on resistance in various materials.

NewtonsHead
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Homework Statement


Well this isn't a homework problem, but I am writing a lab report for a lab we did concerning the change in resistance as a function of temperature.

Everything I have read says that the resistance in conductors should increase with temperature, but all of our data shows that resistance decreases as temperature increases. This was shown in a resistor, commercial resistor, diode, and copper wire. However, the resistance of an inductor DID increase as temperature increased. I don't know why all of our data doesn't support what I am learning. Nothing about our experiment would have yielded such results so I think I may be understanding it the wrong way.

The only reason I can think of is that our components were somehow semi-conductors because the resistance of semi-conductors decreases as temperature increases just like our data.

Anyone know what's going on?
 
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The resistance of the copper wire should have increased with temperature.

But for resistors, that depends on how they're made. Precision resistors are actually a blend of two (or more?) materials, one of which has a + temp. coefficient and one a -. The mfr. tries to blend the mixture to get zero coeff but obviously they're going to miss on either side by some amount.

A diode doesn't have 'resistance ' per se because its i-V characteristic is not linear. But in the expression i = i0 exp(V/VT), VT = kT/q so obviously that affects the i-V curve. (q=electronic charge k = Boltzmann constan, T = kelvin temperature).

No telling what the inductance should have done with temperature.
 
It seems that the resistors we used had a negative temp. coefficient which is weird. All I can do is blame how the parts were made?
 
NewtonsHead said:
It seems that the resistors we used had a negative temp. coefficient which is weird. All I can do is blame how the parts were made?

Either that or what we in the trade call "ESO" = "equipment smarter than operator"! :smile:

I would lean toward the latter, unfortunately, since you found a negative temp. coefficient for the copper wire.
 
No offense taken but does that imply that we just used the equipment wrong or that the equipment malfunctioned? I still have to compare results with others who did the experiment to see if this was common.
 
Without knowing more about your setup I'm afraid I cannot judge on that.

The more you describe the details of your setup the more likely it is that I can help out.
 

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