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Electrical Theory Period 1 SAIT-Alberta > Conductors > Flashcards

Flashcards in Conductors Deck (20)
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1

What is the area of a #10 awg conductor?

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

5.26 mm2

3.27 Ω

2

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

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

Square the diameter

Area is in circular mils.

3

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

26% change.

4

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

5% from service to utilization

3% on a branch circuit or feeder conductor.

5

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

  • 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

6

What are three common materials found in conductors?

What are three uncommon conductor materials?

  • Copper
  • Aluminum
  • Steel

 

  • Silver (least resistant, most conductive)
  • Gold
  • Tin

7

What differentiates a good conductor from a poor one?

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

8

What is dielectric strength?

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

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

  • Measured in Volts/millimetre

9

What are two common semiconductor materials?

  • Silicon
  • Germanium

10

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

What is the temperature coefficient of these two materials?

  • Cu= 1.72•10-8 Ω•m
  • Al= 2.83•10-8 Ω•m

 

  • α= 0.0039

11

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

R = (ρ•L)/A

R2 = R1•(1+α•(T2-T1))

12

What are some of copper's applications?

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

13

Aluminum's "_____" makes it well suited for outdoor overhead service conductors to buildings.

Light weight.

14

What is steel typically used for as a conductor.

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

15

When should stranded conductors be used instead of solid?

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

16

What four factors affect the resistance of a conductor?

Material

Area

Length

Temperature

17

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

Small (like Nichrome II for oven elements)

18

How can one measure the diameter of a conductor?

By using callipers or a micrometer

19

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

A = π•r2 (where r = radius)

20

How is optical cable constructed?

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.