Conductors

Question 1

What is the area of a #10 awg conductor?

What is it’s resistance at a length of 1000 meters?

Answer 1

5. 26 mm²
6. 27 Ω

Question 2

How does one determine the area of conductors larger than 4/0?

Answer 2

Determine diameter in mils (1/1000 of an inch).

Square the diameter

Area is in circular mils.

Question 3

What is the percent change in area or resistance of a conductor when sizing up or down 1 awg size?

Answer 3

26% change.

Question 4

What is the maximum allowable percentage voltage drop on line conductors?

Answer 4

5% from service to utilization

3% on a branch circuit or feeder conductor.

Question 5

What are some advantages of optical cable over electrical when transferring data?

Answer 5

• No grounding or voltage problems
• Light is immune to electromagnetic interference
• Light does not generate any “noise”
• Optical cable can handle much more data/second

Question 6

What are three common materials found in conductors?

What are three uncommon conductor materials?

Answer 6

• Copper
• Aluminum
• Steel
• Silver (least resistant, most conductive)
• Gold
• Tin

Question 7

What differentiates a good conductor from a poor one?

Answer 7

A good conductor has more free electrons per cubic centimetre of material than a poor conductor.

Question 8

What is dielectric strength?

Answer 8

The applied voltage per thickness of material (millimetres) to cause breakdown.

In other words: A material’s electrical insulating strength.

• Measured in Volts/millimetre

Question 9

What are two common semiconductor materials?

Answer 9

• Silicon
• Germanium

Question 10

What is the resistivity of copper and aluminum at 20 degrees celsius, respectively?

What is the temperature coefficient of these two materials?

Answer 10

• Cu= 1.72•10^-8 Ω•m
• Al= 2.83•10^-8 Ω•m
• α= 0.0039

Question 11

What are the two formulas used to determine resistance of a conductor?

Answer 11

R = (ρ•L)/A

R₂ = R₁•(1+α•(T₂-T₁))

Question 12

What are some of copper’s applications?

Answer 12

• Conductors for residential, commercial and industrial buildings
• Busbars for splitters, motor control centres and panel boards
• Windings for motors, relays, contactors and transformers

Question 13

Aluminum’s “_____” makes it well suited for outdoor overhead service conductors to buildings.

Answer 13

Light weight.

Question 14

What is steel typically used for as a conductor.

Answer 14

• A bonding conductor as conduit, tubing and boxes.
• In neutral supported cable; steel is part of the neutral conductor.

Question 15

When should stranded conductors be used instead of solid?

Answer 15

When large conductors are to be pulled into raceways or when flexibility in the wires is required.

Question 16

What four factors affect the resistance of a conductor?

Answer 16

Material

Area

Length

Temperature

Question 17

A conductor with a smaller temperature coefficient would have a relatively “_____” change in it’s resistance as it heats up.

Answer 17

Small (like Nichrome II for oven elements)

Question 18

How can one measure the diameter of a conductor?

Answer 18

By using callipers or a micrometer

Question 19

How can one find the cross sectional area of a circle?

Answer 19

A = π•r² (where r = radius)

Question 20

How is optical cable constructed?

Answer 20

Tiny plastic optical fibres (individually coated with a reflective cladding) isolated from each other in a bundle.

Then, covered with a material suitable for the application environment.