- #1

Vaclav

- 10

- 1

## Homework Statement

After performing a lab experiment to determine the conductivity if Pasco conductivity paper, I found the conductivity to be 0.195 Ωm. We found conductivity by graphing measured values of voltage (y axis) and the length (x axis) between the probes of a voltmeter that are touching the conductivity paper. We know that the slope that equals ( rho * I ) / A, so using our measured values for current and cross sectional area, we can solve for resistivity. Doing so tells us that resistivity = 5.13 Ωm. Taking the inverse gives us conductivity. As a step in the lab in the lab report I must write, I must compare it to the manufacturer's value, which is given as 5000 Ω per square. I have read that the resistivity is equal to the sheet resistance multiplied by the thickness of the material. Thus, the manufacturer says that the resistivity = 62.5 Ωcm = 0.625 Ωm. The professor who supervised this experiment says that most of the class got around my value for resistivity and checked our units to make sure that units are not the issue. Thus, I am wondering what could could be going on that makes our value different by more or less 10 times.

Thickness: t = 0.0125 cm

Width: w = 2.12 cm

Current: I = 1.05 * 10^-7 A / S

Slope = 0.204

## Homework Equations

A = width * thickness

V = IR

V = (resistivity * length / A) * I

V = (rho * L / A ) * I

V = (rho * I / A) * L ---> for graphing, since we do not change the current, cross sectional area, or resistivity, and we change the length between probes.

Slope = ( rho * I ) / A

rho / t = sheet resistance

## The Attempt at a Solution

I have been attempting to figure out why our number is essentially off by a factor of ten by converting all measurements to centimeters in case the manufacturer did. I have also tried converting their 5000 Ω per square value (which is the resistance of a sheet w wide and L long) by adjusting the "square" that they use to fit the geometry of our sheets (we cut the original sheet into long strips). Originally, the sheets were 28 cm by 20 cm, with squares on the paper being 1 by 1 cm. After cutting, the sheets were 28 cm by 2.12 cm. I posting this to see if there is some piece of information that I am missing when comparing/converting sheet resistances.