PhysicsLAB: Resistance, Gauge, and Resistivity of Copper Wires

During class we measured the lengths (each were approximately 9 feet) and diameters of several gauges of solid copper wire. Unfortunately our ohm-meters did not have sufficient sensitivity to measure the resistance of our samples.

Independent of buying a new ohm-meter, what could have been done to get a measureable resistance? Our meters were sensitive to 1/10th of an ohm. Be specific.

What did you have to do to the higher gauged, insulated (enameled) wires before measuring their diameter and attempting to measure their resistance?

What instrument did you use to measure the diameter of these very small wires?

Refer to the following information for the next two questions.

Given below is a table of a sample of the lengths and diameters of different gauges of solid copper wire.

Given the diameter, discuss the mathematical steps needed to calculate the cross-sectional area of the each wire.

What is the relationship between a wire's diameter and its gauge?.

Refer to the following information for the next two questions.

Borrowing a more sensitive meter, a measurement for the resistance of each wire was later obtained. The results are shown in the table below.

Why was the column of resistance per unit length calculated?

Based on the graph shown below, what can be determined regarding the relationship between the resistance per unit length of each wire and the cross sectional area of each wire?

Refer to the following information for the next five questions.

To rectify this data, the next step was to plot R/L vs 1/A.

Based on this graph, what is the resistivity of copper?

If the accepted value is 1.72 x 10^-8 ohm-m, what was the group's percent error for this lab?

Based on your resistance measurement difficulties, when wiring sample circuits in labs do you need to be concerned about the lengths or the diameters of the connecting wires? Explain.

As shown in this picture, copper wire comes both solid and stranded.

Why for this lab did the teacher choose to not use samples of stranded wire?

During the "late 1960's and early 1970's aluminum was sometimes used by builders to wire homes." Why was this practice discontinued since aluminum is so much cheaper than copper? The answer is presented within the first two pages of this article: http://apps.geindustrial.com/publibrary.