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Conductors and Insulators
11 questions By Tony R. Kuphaldt
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Question 4 of 11
Identify several substances that are good conductors of electricity, and several substances that are good insulators of electricity.
Reveal answerIt is very easy to research (and test!) whether or not various substances are either conductors or insulators of electricity. I leave this task in your very capable hands.
Notes:If students have access to simple multimeters, they may perform conductivity tests on various substances with them. This is a fun and interesting classroom activity!
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Question 5 of 11
What naturally occurring substance is the best conductor of electricity?
Reveal answerMost people think the answer to this question is gold. However, there is another type of metal that conducts electricity better than any other type of metal, including gold! Document where you found your answer to this question.
Notes:A few of your students may come across superconductors in their research, which of course conduct electricity perfectly (with no resistance to electric current whatsoever). However, the answer I’m looking for here is the non-superconducting metal with the lowest electrical resistance of all.
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Question 6 of 11
Electrical wire is often rated according to its cross-sectional diameter by a gauge scale. Which is the larger-diameter wire size, 14 gauge or 8 gauge?
Reveal answer8 gauge is the larger diameter.
Notes:For students familiar with shotguns, the methodology of the wire gauge scale makes sense. For just about everyone else, the gauge scale seems “backward.”
For 10.
I used the second entry for Mica, phlogopite, at https://www.engineeringtoolbox.com/dielectric-strength-electrical-insulator-d_2185.html
with a dielectric strength of 31.5 E6 V/m.
My calculation using dimensional analysis: 50 mm x (10 E-3 m/1 mm) x (31.5 MV/m) = 1.58 MV
This is way off from 1 kV - what went wrong?
For 11.
Could you just take a battery, two wires, a small and measured piece of the insulator, and connect one of the wires to one end of the material and then the other wire to the other end, and bracket the voltage from ammeter readings until a small enough range is found for the voltage at which the insulator becomes a conductor? Taking account of the size of the material, of course.
As for the measurement of V/m - is the measured distance for m from one end of the circuit to the other, rather than any particular length of the piece of material?