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