Objective 425.1 Worksheet

Determine the resistance, in ohms, of a 100 watt, 120-volt incandescent light bulb.

144 ohms

What is the ac resistance of 500 feet of 1000 kcmil aluminum wire in a steel conduit?

.0125

A 90-ampere, 240-volt, single-phase load is located 225 feet from a panelboard and is wired with 3 AWG THWN copper conductors. What is the approximate voltage drop on the conductors? (K = 12.9)

10

At 75ºC, what minimum size THWN copper conductors are required (without exceeding NEC® recommendations) to feed a 1/4-horsepower, 115-volt, single-phase motor located 230 feet from the source? Use K=12.9

10

10 AWG circuit conductors will be run from a 1-pole circuit breaker in a 120/240-volt, 1Ø, 3-wire panelboard to a 14.1-amp 120-volt load. The load can be located a maximum of ___ feet from the panel. Use K = 10.98 and limit the voltage dropped in the circuit conductors to 3%.

120

An 80-ampere, 240-volt, single-phase load is located 200 ft. from a panelboard and is wired with 3 AWG THWN copper conductors. What is the approximate voltage drop of the conductors? (K = 12.9)

7.84

A load can be located a maximum of ___ feet from the panel. From a 2-pole circuit breaker the 8 AWG circuit is run out to a 45.6-amp 208-volt load. The breaker is installed in a 120/208-volt, 3Ø, 3-wire panelboard. Use K = 11.6 and limit the voltage dropped in the circuit conductors to 2.2%.

71

A three-phase, 480-volt, 100-amp load is located 390 feet from a panelboard. What minimum size THWN aluminum conductor is required to limit the voltage drop to 3 percent? (K = 21.2)

1/0 AWG

What is the voltage drop percentage on two 10 AWG THW, uncoated copper, stranded branch-circuit conductors, 120-feet long, supplying a 21-ampere, 240-volt load?

2.6

A 120-volt branch circuit has only six 100-watt, 120-volt incandescent luminaires connected to it. In the "home run" (circuit) supplying this load, the total measured current will be ___.

5 amps

A three-phase, 480-volt, 90-amp load causes a 2.5% voltage drop in the circuit conductors. The circuit conductors are 1 AWG THWN copper. (K = 11.2) What is the length of the circuit between the panelboard and the load?

575

Two one-ohm resistors are in parallel. The total resistance ___.

is 1/2 ohm

A 13.9-amp, 240-volt load is connected to a 2-pole circuit breaker in a 120/240-volt, 1Ø, 3-wire panelboard using 12-2 AC cable. Use K = 11.3 and limit the voltage dropped in the circuit conductors to 2.5%. The maximum length of the cable that can be used for the circuit is ___ feet.

124