SIMPLE CONCEPT OF CONDUCTORS AND INSULATORS

BY CREANOVA ENGINEERS…www.creanovaengineers.blogspot.in

CONDUCTORS AND INSULATORS

Question 1

What is the difference between materials classified as conductors versus those classified as insulators, in

the electrical sense of these words?

Electrical ”conductors” offer easy passage of electric current through them, while electrical ”insulators”

do not. The fundamental difference between an electrical ”conductor” and an electrical ”insulator” is how

readily electrons may drift away from their respective atoms.

For an illustration of electron mobility within a metallic substance, research the terms electron gas and

”sea of electrons” in a chemistry reference book.

Question 2

Identify several substances that are good conductors of electricity, and several substances that are good

insulators of electricity.

It 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.

Question 3

What naturally occurring substance is the best conductor of electricity?

Most 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.

Question 4

Given two lengths of metal wire, which one will have the least electrical resistance: one that is short,

or one that is long? Assume all other factors are equal (same metal type, same wire diameter, etc.).

The short wire will have less electrical resistance than the long wire.

Question 5

Given two lengths of solid metal wire with round cross-sections, which one will have the least electrical

resistance: one that is small-diameter, or one that is large-diameter? Assume all other factors are equal

(same metal type, same wire length, etc.).

The large-diameter wire will have less electrical resistance than the small-diameter wire.

Question 6

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?

8 gauge is the larger diameter.

Question 7

What disadvantages might there be to using undersized wire in an electrical power distribution system,

where electricity is transmitted from generators (sources) to ”loads” (devices requiring power) far away?

What might happen if the wires we choose for this application were to have insufficient cross-sectional area?

An analogy: what would happen if the water pipes in a municipal water supply system were sized too

small?

Question 8

What disadvantages might there be to using oversized wire in an electrical power distribution system,

where electricity is transmitted from generators (sources) to ”loads” (devices requiring power) far away?

What might be bad about using wires with more than sufficient cross-sectional area for the purpose?

An analogy: what would be bad about using oversized water pipes in a municipal water supply system?

Nothing, perhaps, once the system was operational. However, what about the cost of building the system?

Question 9

What does the breakdown voltage (also known as dielectric strength) rating for an electrically insulating

substance mean?

The breakdown voltage, or dielectric strength, rating of an insulator is the maximum amount of applied

voltage it may withstand per unit thickness without conducting appreciable current.

Question 10

How much voltage can a 50 mm thick piece of mica withstand before breaking down?

Approximately 1000 volts, or 1 kV.

Question 11

Design a circuit to test the breakdown voltage of a material.

I won’t provide you with a ready-made schematic diagram for such a circuit, but I will give you a hint.

If a substance were to be subjected to a voltage in excess of its dielectric strength, what effect(s) would

indicate breakdown?

BY CREANOVA ENGINEERS…www.creanovaengineers.blogspot.in