A1-15 & 16

• What is a mil?

  1/1000 of an inch
• Formula for CMA

  CMA = d^2
• The larger the AWG number, the ____ the resistance per unit length of the wire

  greater
• The ratio of the cross-section in circular mils of one gauge to that of the next higher gauge number is

  1.26
• bus-bars have ___ cross-sections

  rectangular
• How do you calculate CMA if you have SMA?

  Take the SMA and multiply by 4/pie
• How do you calculate SMA if you have CMA?

  Take the CMA and multiply by (pie/4)
• What is the relationship between the area of No. 1 wire and No. 4 wire?

  No. 1 wire is twice as large as No. 4 (every three you go up on AWG size, it is 2 times smaller)
• What are factors affecting resistance?

  1. Natural resistance (k) of material
  2. length of wire
  3. cross-sectional area of wire
  4. Temperature
• The ideal electrical conductor is a material that will carry the ____ amount of current with the ____ amount of temperature rise

  greatest...least
• Formula for R of a conductor?

  R = k*L / CMA
• K for Aluminum

  17
• K for copper

  10.4
• What is the temperature coefficient of resistance?

  The percentage of resistance change per degree of temperature change from 20 degrees Celcius
• What is meant by 'the temperature coefficient of resistance of copper is 0.00393?'

  for every degree the temperature of copper rises above 20, the resistance increases by 0.393 of 1 percent of its value at 20
• what is a positive temperature coefficient?

  an increase in temperature leads to an increase in resistance (conductors have this)
• what is a negative temperature coefficient?

  a rise in temperature causes a drop in resistance (this happens for semi-conductors and most insulators)
• What is the temperature coefficient for aluminum?

  0.0039
• what is the temperature coefficient for copper?

  0.00393
• what does temperature coefficient of zero mean?

  resistance is independent of temperature