Measured Surface Resistivity Much Higher than Theoretical Value (Why?)

In summary, the conversation revolved around a physics lab experiment to measure the surface resistivity of a conductive paper with a carbon filler. The theoretical Rs value for this paper is approximately 5,000 Ω/☐, but the calculated Rs values were found to be much higher at 10,100 +/- 83.07 Ω/☐ and 11,220 +/- 63.02 Ω/☐ when varying length and width, respectively. The group could not explain this large discrepancy and questioned if it was due to the flow of electrons being blocked or if there were errors in their setup. They also discussed the importance of following proper procedures and understanding the theoretical resistivity calculation. They also noted that a sheet
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LulaBell
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Thread moved from the technical forums to the schoolwork forums
I recently conducted a physics lab to measure the surface resistivity of a conductive sheet of a paper with a carbon filler. The theoretical Rs is approx. 5,000 Ω/☐ for this paper and yet we have calculated two Rs values:

Rs when Varying Length and holding Width = 10100 +/- 83.07 Ω/☐
Rs when Varying Width and holding Length = 11220 +/- 63.02 Ω/☐

To me, this discrepancy is very large, and I can't seem to explain why it could even occur, although we are not the only ones measuring this almost double Rs, it seems consistent around 10,000 Ω/☐ across the entire lab and yet I can't figure out why that is. Does it have something to do with the flow of electrons being blocked? Perhaps we did not connect something right although I struggle to see how that would be consistent with other groups.

Any help is very appreciated.
 
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So what measurement procedures did you use? How does your setup method compare to how the paper is typically used in practice?
 
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Yes the procedures that you followed are important. Also, what do you mean by "theoretical" resistivity? Do you know the model that has been used to calculate it? There might be a factor of 2 in the calculation (and the measurement) that was made to determine it vis-à-vis the way you conducted and analyzed your measurement. Remember that a sheet of paper has two surfaces.
 
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Do you have any additional details that may be useful @LulaBell ?

Or were you able to resolve the discrepancy?
 

1. Why is the measured surface resistivity much higher than the theoretical value?

There are several possible reasons for this discrepancy. One possibility is that there are impurities or defects in the material that contribute to higher resistance. Another possibility is that the material is not in its ideal state, such as being too thick or too thin, which can affect its resistivity. Additionally, the measurement technique used may not be accurate enough to capture the true resistivity value.

2. How does surface roughness affect the measured surface resistivity?

Surface roughness can play a significant role in the measured surface resistivity. A rougher surface can have more contact points between the material and the measuring device, leading to a lower resistance value. On the other hand, a smoother surface may have fewer contact points, resulting in a higher resistance value.

3. Can temperature affect the measured surface resistivity?

Yes, temperature can have a significant impact on the measured surface resistivity. As temperature increases, the resistance of a material typically decreases, leading to a lower measured resistivity value. This is due to the increased movement of electrons, which results in a decrease in resistance.

4. What role does the material composition play in the measured surface resistivity?

The material composition can greatly impact the measured surface resistivity. Different materials have different levels of conductivity, which can affect their resistance. For example, metals generally have lower resistivity values compared to insulators, which have higher resistivity values.

5. Are there any external factors that can affect the measured surface resistivity?

Yes, there are several external factors that can impact the measured surface resistivity. These include humidity, pressure, and exposure to certain chemicals. These factors can alter the material's properties and ultimately affect its resistivity. It is essential to control for these factors when conducting resistivity measurements to obtain accurate results.

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