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Not only is this question practical from the standpoint of understanding circuit function, but also from the perspective of electrical safety. Why is it important for wires to be insulated? Are overhead power lines insulated like the wires used in classroom projects? Why or why not? How were electrical wires insulated before the advent of modern plastics technology?

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This question affords the opportunity to discuss electrical safety with regard to clothing (often made of cotton). Does dry clothing offer insulation to electricity like the old-style cotton wire insulation? Can cotton clothing be trusted to insulate you safely from hazardous voltage?

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For students familiar with shotguns, the methodology of the wire gauge scale makes sense. For just about everyone else, the gauge scale seems "backward."

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NEC code books are rather large, so students may feel inclined to limit their answers to what is included in the Änswer" for this question. However, you should challenge them to look deeper into an NEC book and discover the wealth of information contained therein.
Specifically, ask them to describe some of the Ärticle" topics typically found in an NEC book.

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A good follow-up question to this would be to ask, "What are some of the advantages and disadvantages of solid versus stranded wire?" Challenge your students to consider such issues as cost, physical flexibility, and ease of connections.

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It is important that students know where to look for information like this, because they will surely come across unique wire types in their later experience, and will need to know how to identify the wire.

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Be sure to ask your students what resource(s) proved helpful in researching the answer to this question. Being essentially a safety issue, there are several industry publications on electrical safety regulations that may prove informative.
This question connects several important principles together: physical ratings of materials, power dissipation in metallic conductors, and electrical safety. Challenge your students to "connect" these principles on their own by probing their knowledge with follow-up questions.

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Wire gauge numbers and diameters for this table were taken from table 2-85 of the American Electrician's Handbook (eleventh edition) by Terrell Croft and Wilford Summers. Area in circular mils for each AWG size was calculated from the given diameter.

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Although this rule is only approximate, it is useful to know!

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If you happen to have pieces of conduit available for demonstration, show them to your students during discussion time. Better yet, take them to a place where they can see electrical conduit in use!
Be sure to ask them questions about the other methods (raceways, wire trays) of laying wire, and how these methods compare with rigid conduit.

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Ask your students to describe possible applications for busbars. Where would they typically encounter such huge conductors of electricity?

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Explain how this is analogous to the ßquare inch" being defined as the area of a square measuring one inch on a side. If you need to approach the definition in smaller conceptual steps, you might want to first define what a "circular inch" is before you define what a "circular mil" is.

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Calculating the cross-sectional area of the 1 ×2 busbar in units of circular mils may be challenging for some students, because an equation directly relating linear dimensions to circular mil area may not be easy to obtain. However, even in the event that no equation can be found, there is a way to solve for the busbar's area in units of circular mils by observing the answers obtained for the other two conductors' areas.

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Show your students a wire gauge table, if their textbooks do not already contain one.

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Students who have worked with power tools, especially on construction sites where long extension cords are commonly used, will be familiar with this phenomenon. Ask your students what effect different gauges of wire in the extension cord would have on this degradation of drill motor performance. Also, ask about different lengths of extension cord. What, exactly, is the electrical quantity that varies with these dimensional changes, that causes the drill motor performance to vary?

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The purpose of this question is to get students to kinesthetically interact with the subject matter. It may seem silly to have students engage in a ßhow and tell" exercise, but I have found that activities such as this greatly help some students. For those learners who are kinesthetic in nature, it is a great help to actually touch real components while they're learning about their function. Of course, this question also provides an excellent opportunity for them to practice interpreting component markings, use a multimeter, access datasheets, etc.

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