Lesson 110 - Voltage Drop, Cable, Conduit, and Tubing
A branch circuit for a copy machine has 124 volts available at the circuit breaker. Because the copier draws 15.4 amps, there is a total of 13.2 volts dropped in the branch circuit conductors. With the copier operating, the voltage that would be measured at the receptacle where the copy machine is connected would be ___ volts.
110.8
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
EMT shall be securely fastened in place at least every ___. In addition, each EMT run between termination points shall be securely fastened within ___ of each outlet box, junction box, device box, cabinet, conduit body, or other tubing termination.
3 m (10 ft), 900 mm (3 ft)
The Code recommends a voltage drop no greater than ___ percent for feeders and no greater than ___ percent total for feeders and branch circuits together.
3% and 5%
What is the voltage drop on a 120-volt circuit consisting of 10 AWG copper wire where the load is 30 amps and the distance between the panel and the load is 50 ft? (Use K=12)
3.46
According to the NEC®, what is the largest size of flexible metallic tubing (FMT) that can be used?
3/4 inch
___ is the Code Article that provides the requirements for Type AC cable.
320
The NEC® requirements for securing Type AC cable entering or exiting a box are located in Section ___.
320.30
The NEC® requirements for securing Schedule 40 PVC in horizontal runs are located in Section ___.
352.30
You have to run a 240-volt circuit to a 24-amp load that is located 321 feet away from the panel. The smallest size wire you can pull in for the circuit is ___ AWG. The voltage drop can't exceed 4.8 volts. Use K = 10.9.
4
Voltage drop problems can be caused by any of the following conditions: • wire too small for load served • circuit conductors too long • poor or corroded connections at terminals • conductors operating at high temperatures (higher temperatures increase resistance) The presence of one or more of these conditions causes an increase in the total ___ of the circuit.
Resistance
The support requirements for ENT are located in the NEC® in Section ___.
362.30
When doing voltage-drop calculations, where is the cross-sectional area in circular mils located?
Chapter 9, Table 8
When Type MC cable is installed in horizontal runs through the holes in sheet metal studs and joists, do additional supports have to be installed (Caddy clips for example)? The MC cable is securely fastened within the required distance from any boxes or enclosures and the framing members are on 24" centers.
No
Which of the following wiring methods provides the best protection against physical damage?
Rigid
Trade size 1 Schedule 40 and Schedule 80 PVC use the same fittings (couplings and connectors).Note: PVC "connectors" are properly identified as male or female adapters.
True
When MC cable is used as the wiring method, the fittings used with the MC cable are required to be listed for MC cable.
True
A 3-foot long piece of LFMC (liquidtight flexible metal conduit) will be installed to connect a motor that is going to vibrate. Does the NEC® require that a separate equipment grounding conductor be installed?
Yes
A 4-foot long piece of FMC (flexible metal conduit) will be installed to connect a motor that is going to vibrate. Does the NEC® require that a separate equipment grounding conductor be installed?
Yes
When circuit resistance is increased, such as when corrosion develops at wire nut terminations, the flow of electrons in a circuit is ___.
decreased
As the length of wire in a circuit increases, the circuit resistance ___.
increases
The voltage (volts) dropped in circuit conductors ___ when the circuit length is increased.
increases
When connections to motorized appliances such as food waste disposers, washers, dryers, air-conditioners, and heat pumps that may be subject to vibration are made, ___ is an acceptable choice for the wiring method.
liquidtight flexible nonmetallic conduit
Alflex® Type NM liquidtight flexible nonmetallic conduit can be installed ___.
outside in the sunlight where the temperature is -15°F in a concrete slab
The maximum distance permitted between a box and the first strap (support) for an installation using 1" LFMC (liquidtight flexible metal conduit) is ___ ft.
1
What size equipment grounding conductor is contained in 10-3 Type MC cable?
10
Cables run parallel to (along) or through holes bored in framing members must be at least ___ from the edge of the framing member.
11/4 inches (32 mm)
In the NEC®, voltage drop for branch circuits is covered in ___.
210.19(A) I-Note 4
What is the cross-sectional area, in circular mils, of a copper conductor needed to supply a circuit 75 feet from the panel, with a load of 50 amperes and a voltage drop not to exceed 3.5 volts? (Use K=12)
25,714
Using 12-2 MC cable with interlocked armor that has an overall diameter of 1/2", what is the minimum dimension as shown at ? in Figure 110.12?
3 1/2"
Horizontal runs of trade size 3 Schedule 40 PVC conduit must be supported at ___ ft intervals.
6
What is the maximum distance permitted between straps (supports) where 12-2 Type MC cable is run for some distance between boxes or enclosures? ___ feet
6
What is the percentage of voltage drop on a 120-volt circuit? 12 AWG copper conductors were used and the load draws 20 amperes. The distance from the panel to the load is 100 feet. Use K = 12 to calculate the voltage dropped in the conductors.
6%
What is the voltage drop on a 120-volt circuit? The circuit uses 12 AWG copper conductors and has a load of 20 amperes. There is a distance of 100 feet from the panel to the load. (Use K=12)
7.35 volts
For Type MC cable, is the insulated green conductor permitted to be used as a current-carrying circuit conductor?
No
Support and physical protection requirements for Type AC cable are similar to those for ___.
Type NM cable