Lesson 4: Conductors, Conductor Resistance, and Wattage Loss

c. specific resistance

The resistance of a conductor is directly proportional to its length and ? and inversely proportional to its cross sectional area.

c. There is less resistance in the 100-ohm filament. Therefore, more current will flow, causing more heating and incandescent action.

Why will a lamp with a 100-ohm filament burn brighter than a lamp with a 300-ohm filament?

1.27

If a 250-foot #12 copper conductor has a resistance of 0.397 Ω, how much is the resistance of the same conductor at 800 feet? (Round the FINAL answer to two decimal places.)

a. American Wire Gauge (AWG)

In the United States, conductors are sized according to the ? standard or by the actual number of circular mil (CM) for the wire.

d. voltage / power

Lamps have both a ? rating and a ? rating.

479.29

You wish to use #18 tungsten wire at 20°C to make a 10 Ω resistor. What length of wire will be required for this job? Hint: Be sure to use the K value found in the reference. (Round the FINAL answer to two decimal places.)

18.69

Calculate the resistance of a piece of aluminum wire with a diameter of 100 mils and a length of two miles, at 68°F. Hint: Be sure to first convert mils to cmils and use the K value for aluminum found in the reference. (Round the FINAL answer to two decimal places.)

d. resistance

Different wattage ratings are achieved for lamps with the same voltage rating by changing the value of the ? .

c. 1,000 watt hours

Each kilowatt hour equals ? .

False

Electrical energy usage is measured in volt-amperes.

b. Measure the diameter of the conductor in inches. Multiply the result by 1,000; then square it.

Explain how to calculate the approximate cross-sectional area of a conductor in circular mils.

490.87

Find the cross-sectional area of a conductor in millimeters squared when the diameter of the conductor is 25 millimeters. Pi must be calculated as 3.14159. (Round the FINAL answer to two decimal places.)

True

The measurement kilowatt-hour expresses how much energy is used over a period of time.

b. kilowatt-hour

The unit of measurement used by electric companies to determine a monthly electric bill is the ? .

True

The unwanted heat generated by an incandescent lamp is considered a power loss.

a. circular mils

The cross-sectional area of American conductors is expressed in units called ? .

True

The higher the resistance, the lower the rated wattage of a lamp.

d. Resistivity

Specific resistance is also called ? and is abbreviated with the capital letter K or the Greek letter ρ (rho).

c. #10 (AWG)

What is the approximate gauge of a wire that has a diameter of about 100 mils?

D

What is the formula for calculating the resistance of wire?

D

What is the formula to find the cross-sectional area of a cable in square inches?

D

What is the formula to find the voltage drop of the conductors to and from the load?

A

What is the formula used to find the line loss?

1.91 Ohms

What is the resistance of a 600-foot #12 (solid) aluminum conductor? Hint: The resistance of the conductor is 3.18 Ohms/1000 feet. (Round the FINAL answer to two decimal places.)

e. Voltage rating of the conductor

Which of the following is not a characteristic that determines the resistance of a conductor?