Lesson 106 - Applied Math, Ohm's Law, Electrical Symbols, Boxes, and Box Fill Reading Worksheet

314.24

Calculating and providing the proper volume of a box is not always enough. Section ___ of the NEC ® states outlet and device boxes shall be deep enough so that conductors will not be damaged when installing wiring devices or equipment.

trade size 3/ 8

Common switch and outlet boxes are available with all the following size knockouts, except for ___.

4,536

3.5 square yards = ___ square inches

2.25

324 square inches = ___ square feet

5,184

72 2 =

III

As shown in Figure 107.31, ___ is referred to as a "brick" box.

I

As shown in Figure 107.32, ___ is referred to as a "handy" box.

V

As shown in Figure 107.33, ___ is referred to as a "2-gang bell box."

IV

As shown in Figure 107.33, ___ is referred to as a "switch" box.

II

As shown in Figure 107.33, ___ is referred to as a "tile ring."

I

As shown in Figure 107.34, ___ is referred to as a vertical weatherproof GFCI cover.

IV

As shown in Figure 107.35, ___ is referred to as a blank "handy" box cover.

1,090

Figure 107.1315 is the floor plan for a building. The plan has a rectangular area with a right-triangle-shaped area on the left end and a square-shaped area above the right side. Using all the necessary formulas, the total floor area is ___ ft 2.

4

How many number 10 AWG conductors may be installed in a 3" × 2" × 2" device box?

2

How many single receptacles can be installed in a two-gang box that is made using two single-gang boxes that are ganged together?

1302

Refer to Figure 107.1313. Dimension A = 42 feet Dimension B = 31 feet The area is ___ ft 2

145

Refer to Figure 107.1313. Dimension A = 42 feet Dimension B = 31 feet The area is ___ yd 2

75

Refer to Figure 107.1314. Dimension D = 117 inches The area is ___ ft 2

8.3

Refer to Figure 107.1314. Dimension D = 117 inches The area is ___ yd 2

24.75

Refer to Figure 107.456. The minimum volume required for this box is ___ in 3. Each of the three Type NM cables contains a ground. The "pigtails" to the receptacle are 12 AWG wires. As you can see, the cable connectors are external (outside the box).

10.3

Refer to Figure 107.459. You measured Box #3 and it has a depth of 1 1/ 2 inches. The volume is ___ cu in for this box per the NEC ®. Select answer N/A if Table 314.16(A) does not apply to this type of box.

True

Before removing lockout/tagout devices, you must make sure the danger area is clear of tools and workers.

1/ 8 inch 3/ 16 "

Boxes are to be mounted in non-combustible walls so that the box is flush with the finished wall surface. However, the NEC ® permits these boxes to be set back ___ from the finished wall surface.

6

Branch-circuit conductors at outlet boxes are required to have at least ___ inches of free conductor for making splices and connections. The length of conductor is measured from the point in the box where it emerges from its raceway.

47.25

The 3-gang masonry box shown in Figure 107.458 will have several EMT conduits connected to it. The EMT will be the equipment grounding conductor - NO ground wires will be pulled in. The box will contain three 4-way switches. Twelve "travelers" are pulled into the box along with two other circuit conductors. All conductors are 12 AWG copper THHN/THWN. The box must have a minimum volume of ___ in 3.

2.6736

The current drawn by a blender is ___ when operated at 110 volts. The nameplate shows that the blender is rated to deliver 350 watts @ 120 volts.

25

The minimum cubic inch capacity of the j-box (shown in Figure 129.110) you could use where circuits A17-19 (2 "hots" + a neutral") enter the box is ___ in 3. The circuits are tapped and continue to feed other equipment or outlets. The wiring method is 10 AWG MC cable with a 10 AWG grounding conductor. All cable connectors are of the type that have locknuts to secure the connector to the box. The Equipment Grounding Conductor is NOT shown on the drawing.

is not

Using a wire nut, a neutral that enters a box is connected to another neutral that exits the box. A pigtail is also connected under the wire nut and goes to a receptacle in the box. This pigtail ___ counted in the box fill calculation per 314.16(B)(1).

Switch with pilot lamp

What does the "S p" symbol represent?

1.767 square meters

What is the area of a circle that has a diameter of 1.5 meters?

15

What is the area of a right triangle that measures 5 feet on one side and 6 feet on the other side, as shown at the right?

marked with its cubic-inch volume

When it is ___, a raised plaster cover (often called a plaster ring or mud ring) is permitted to increase the maximum number of conductors permitted in an outlet box.

$939.94

You are going to install a number of up lights in a new triangle-shaped sidewalk as shown below. According to your contract with the owner, you also had to purchase the concrete for the sidewalk. The sidewalk is 5 inches thick and the concrete is $139 per cubic yard. The cost for the concrete is $ ___

33.33

You need to final-tighten the mechanical lugs that connect your feeder conductors to a 600-amp safety switch. You are going to use a torque wrench that is calibrated in pound- feet (lb- ft.). The instruction label in the switch reads "400 lb- in." To satisfy the manufacturer's specifications, you will set your torque wrench at ___ lb- ft.

True

For fair enforcement of safety rules, a worker should know the penalties for failing to follow the rules.

540

For the drawing shown in Figure 107.1406: Dimension X = 6 ft. Dimension Y = 4 1/ 2 yd. and Dimension Z = 80 in. The volume = ___ ft 3

3.556

How many cubic yards of concrete are in a transformer pad that is 8 feet wide, 12 feet long, and 1 foot thick?

Go up

If the voltage is raised in a simple circuit, what will the current do?

There is a flexible wiring method with a separate grounding conductor.

It is permitted to make a surface extension from a cover fastened to a concealed box if which of the following conditions exist?

True

Once stored energy has been released (turned OFF) and lockout/tagout has been applied, you can be sure the equipment won't be re-energized while you are working on it.

inversely

Referring to the Ohm's Law formula I = E ÷ R: In a DC circuit, the current is directly proportional to the voltage and ___ proportional to the resistance.

12.8

The NEC ® permits 20% of the cross-sectional area in a wireway to be occupied by conductors. For an 8" × 8" × 6' long wireway the conductors can occupy ___ in 2.

236

Three 6" × 6" and two 8" × 8" electrical boxes are installed in a wall between two studs. There are ___ square inches of wall area taken up by the boxes.

288

What is the power used by a 12-volt circuit with 24 amperes of current?

8.9286

What is the resistance of a 6' PVC heater if the nameplate supplies the following information: 28 amps 250 volts

41.1429

What is the resistance of a blender if the nameplate supplies the following information: 350 watts 120 volts

True

When you perform maintenance work in a customer's plant, you must learn their company's lockout/tagout requirements.

1,200

Where the room dimensions are 30 feet by 40 feet, the floor area of a room is ___.

.011

512 cubic inches = ___ cubic yards

60

A blueprint is drawn to a scale of 1 inch = 10 feet. The building width measures 6 inches on the blueprint. The building is ___ wide.

2 1/ 2"

A group of five metal switch boxes are ganged together to form a 5-gang box. The box assembly is to have three single-pole switches and two three-way switches installed. The following conductors enter the box assembly: six ungrounded conductors (includes "travelers"), five grounded conductors, three switch legs, and five grounding conductors. Also, five cable clamps are contained in the assembly. All the conductors are 12 AWG. Each of the ganged boxes will have to be 3" × 2" × ___.

11.11

A square concrete equipment pad measures 3 ft.-4 in. on each side. The pad has a surface area of ___ ft 2.

113

A square-shaped warehouse has a floor area of 12,769 square feet. The length of one of the walls is ___ feet.

4,369

A water heater has a nameplate rating of 5 KW @ 230 volts. If the voltage supply to the 5,000-watt element in this water heater dropped to 215 volts, the water heater could deliver ___ watts.

312.5(A) 314.17(A) 110.12(A)

According to ___ in the NEC ®, unused knockouts and other openings in electrical boxes and cabinets are required to be closed.

it reduces the fire resistance of the wall

According to building codes and the NEC ®, unless special provisions are made, electrical wall boxes shall not be mounted back to back in the same stud space in fire-rated walls because ___.

Box

According to the NEC ®, what must be installed wherever outlets are required?

100 watt lamp

All of the following items of electrical equipment are devices, except for a ___.

4.69

An electrical contractor is required to set steel posts (bollards) around a pad mounted transformer. You are going to use 11' long pieces of 8" ( inside diameter) pipe for the posts. How many cu. yd. of concrete will you need to fill 33 of these posts with concrete? One of these posts is shown in Figure 107.1402.

II

As shown in Figure 107.32, ___ is referred to as a "box partition."

4

Box II shown in Figure 107.38 is a ___-gang box.

12.06

You have dug a trench that is 24" wide, 36" deep, and 300' long. A cross-section view of the trench is shown in Figure 107.1410. You have installed THREE 4" PVC Schedule 40 conduits in the trench (this is called a duct bank) on supports. The bottom of each conduit is 2" above the bottom of the trench. The outside diameter of each conduit is 4 1/ 2". You must encase the conduits in red concrete to a depth that is 2" above the top of the conduits. Disregard the volume taken up by the pipe supports. You will need ___ cubic yards of red concrete after deducting for the volume displaced by the conduits. Remember, you have 2 inches of concrete above the conduits + the 41/2-inch conduit + 2 inches of concrete below the conduit.

6 hours 15 minutes

You timed your helper and it took him 2 1/ 2 hours to dig a trench 20 feet long. If you get another helper who will work at the same pace, how much time will it take both of them to dig an additional 100 feet?

720

___ cubic inches are contained in a junction box that measures 10" × 12" × 6" deep.

2 1/ 2

A light switch and a fan switch are to be installed in one 2-gang box. For this box assembly, you will use two 3" x 2" metal device (switch) boxes that you will gang together to form the 2-gang box. The cables entering the box are 12 AWG with ground Type MC cables. A 12-2 feeds power to the box assembly and a 12-3 exits the box assembly to supply the fan/light. The cable clamps are external type clamps. The minimum size switch boxes you will use for this installation are 3" × 2" × ___".

36

An electrician was making $13.50 per hour and worked 40 hours per week. He had bought a new truck and needed to make more money but was turned down for a raise. He got mad and quit and was out of work for two weeks. He is now working at a new job that pays $14.25 per hour. Working 40 hours per week at the new job, how many weeks will he have to work to make up for the pay he lost while out of work?

71.6

An incandescent lamp consumes ___ of power at 110 volts where the manufacturer's stamp on the lamp shows: 100 watts @ 130 volts

18.44

As shown in Figure 107.1303, you must install lights in a new triangle-shaped sidewalk on the jobsite. Your contract requires that this area be poured with concrete around your lights and you will have a concrete contractor do the finishing. If the concrete contractor charges you by the number of square yards of area to be finished, his invoice should be for ___ square yards.

11.1

As shown in Figure 107.1422, a 400-foot-long duct bank (four conduits) is buried in a trench that is 18 inches wide. The conduits are laid in the bottom of the trench and dirt is placed around and a few inches over the top of the conduits. To provide 6 inches of cover over the duct bank, ___ cubic yards of cement-stabilized sand will be needed. After the sand is placed over the conduits, the trench is backfilled with the dirt that was originally removed from the trench.

II

As shown in Figure 107.35, ___ is referred to as a blank "1900" or "4-square" cover.

V

As shown in Figure 107.35, ___ is referred to as a blank industrial cover.

19.46

Eight conduits will be installed in the bottom of a trench and red concrete will be poured around the conduits as shown in Figure 107.1404. The specifications require that the concrete completely surround the conduits. You must order the concrete to fill the bottom of the trench as shown. Deduct the volume occupied by conduits. Each conduit has an outside diameter of 3 1/ 2 inches. The duct bank dimensions are: width = 24 inches height = 13 inches length = 322 feet Concrete to order = ___ yd 3

22.2222

Figure 107.22 represents a drill circuit. What is the resistance of the drill given the following nameplate information? 5.4 amps 120 volts

2.4

How many cubic yards of concrete do you need to order to pour 32 transformer pads that are 35 inches wide by 28 inches long by 3 1/ 2 inches high? Select the closest answer!!!!!

2.4275

How many cubic yards of concrete will it take to pour 4 transformer pads? Two of the transformer pads are 8 1/ 4 feet × 6 3/ 4 feet × 4 inches. The other two are 7 3/ 4 feet × 5 1/ 2 feet × 4 inches.

6.67 min.

If a pump discharges 600 gallons of water in 2.5 minutes, how long will it take to discharge 1,600 gallons of water?

40

If a simple circuit has 480 volts applied with a current flow of 12 amperes, what is its resistance?

False

If a worker is not present to remove his own lock, any co-worker can remove it as long as he first makes sure it's safe.

26 days

If four electricians can install 200 feet of 2-inch conduit in two days, how long will it take them to install 2,600 feet of the same conduit?

Go up

If the resistance is lowered in a simple circuit, what will the current do?

.25

If the simple circuit in Figure 107.201 has 400 ohms of resistance and 100 volts applied, what is its current flow?

Go down

If the voltage is lowered in a simple circuit, what will the current do?

True

If you have to temporarily re-energize equipment while you are working on it, you must re-apply energy release and lockout/tagout as soon as energy is no longer needed in the system.

False

In a lockout, one person is allowed to attach a single lock for an entire work crew.

an extension ring with EMT connected to any knockout

In order that the connections inside an outlet box remain accessible, the NEC ® permits a surface extension from a flush-mounted device box to be made by installing ___.

314.3

Section ___ of the NEC ® permits nonmetallic outlet and device boxes to be installed with nonmetallic sheathed cable.

314.16(B)(4)

Section ___ of the NEC ® states that for each yoke or strap, containing one or more devices or equipment, a double volume allowance shall be made.

35.6

The 4" square (1900 or Raco 232) box shown in Figure 107.433 is 2 1/ 8" deep. A 3/ 4" rise plaster ring (also shown) is installed on the box and will add a volume of 5.3 in 3. This volume is found stamped into the plaster ring. Using the box volume per the NEC ®, the total volume of the assembly with the p-ring installed on the box is ___.

8-32

The mounting holes on the face of box II in Figure 107.36 are tapped for ___ screws.

10-32

The tapped holes in the back of all the boxes in Figure 107.36 are tapped for ___ grounding screws.

3:4

There are 31 students in a class. Eight (8) students are over 6 feet tall. Seventeen (17) students are 5'-6" to 6'-0" in height. Six (6) students are under 5'-2". What is the ratio of the number of students under 5'-2" to the number of students over 6' tall?

9.1667

What is the current drawn by a 7 1/ 4" circular saw if the nameplate supplies the following information and it is operated at 110 volts: 10 amps 120 volts

21.6 kW

What is the power used by a circuit that is operating at 480 volts and pulling 45 amps?

767.290

What is the resistance of an incandescent lamp if the manufacturer supplies the following information: 100 watts 277 volts

37

What is the square root of 1369?

37.5

What is the total cubic inch capacity of three 3" × 2" × 2 1/ 2" device boxes ganged together?

Legend or notations

Where will the explanation for non-standard symbols usually be found?

III only

Which of the boxes shown in Figure 107.31 can be "ganged" together to form a 3-gang box?

4 11/ 16 × 1 1/ 2 square

Which of the following metal boxes could be used for one single-pole light switch (connected to 12 AWGs), six each 14 AWG conductors, four each 12 AWG conductors, and two cable clamps?