wiring 3

A circuit breaker panel, listed as a load center with a main circuit breaker, is installed on an exterior basement wall of a building, as the service entrance for the building. If the panel is 20 inches in width, the minimum width of clear working space required to be provided in front of this service panel is:

30 inches

When there are only 2 conductors installed inside the raceway, the maximum percent fill, of a 10 foot long conduit, is:

31%

Examine the figure below of a "LB" style conduit body. A trade size 2 inch intermediate metal conduit (IMC) enters and leaves the conduit body. The conduit is protecting four size 2/0 copper conductors. Dimension "A" is the distance from the conduit entry to the removable cover. The minimum permitted distance for dimension "A" is:

3½ inches.

A non-dwelling building is supplied with single-phase power at 120/240 volts, from a 3-wire electrical system, with a single 150-ampere rated main circuit breaker. The ungrounded service entrance conductors are aluminum and are size 3/0 AWG and are protected with a raceway. The termination for the neutral conductor is rated 75oC. The calculated load for the grounded neutral conductor is 48 amperes. If the service neutral for the service entrance is aluminum with Type THWN insulation, the minimum size permitted for this service is:

4 AWG

The pull box rules of NEC Section 314.28 only apply when at least one of the conductors in the box is at least a size:

4 AWG.

A circuit powered at 120 volts has an 8 ohm, 12-ohm, and a 24-ohm resistor connected in parallel. The total resistance of the circuit is:

4 ohms 1 1 1 1 1 1 1 ---- = ---- + ---- + ---- = ----- + ---- + ----- = 0.25 RT R1 R2 R3 8 12 24 1 RT = --------------- = 4 ohms 0.25

A panelboard is supplied with a 480/277-volt electrical system. The panelboard is mounted on a wall and the front of the panel faces a concrete wall. The minimum distance from the front of the panelboard to the concrete wall is:

42 inches

The allowable ampacity of a size 7, copper, 2-wire type SO flexible extension cord is:

47A

Equipment ground-fault protection is required to be installed on the service of a commercial building served with a three-phase, solidly grounded:

480/277-volt, wye electrical system 1,000 amperes and larger.

Examine the diagram shown below. If the secondary winding is producing 240 volts, the primary winding is being energized at:

4800 volts

Three-quarter inch rigid metal conduit (RMC) is run across a ceiling perpendicular to the trusses and attached to the bottom of the trusses. The RMC is supported at the bottom of each truss and is connected to the luminaire (light fixture). The maximum permitted distance from the lighting fixture to the first support is:

5 feet

A straight horizontal run of 2-inch rigid polyvinyl chloride conduit (PVC) is run across a concrete ceiling surface of a parking garage and is supported within three feet of a box. The maximum distance permitted between supports for this straight run of conduit is:

5 ft

Unless marked otherwise, a box used to support a ceiling mounted luminaire (lighting fixture), must be able to support a weight of up to:

50 pounds.

If not marked on the device, the interrupting rating of a circuit breaker is assumed to be:

5000A

On a particular branch circuit, it is determined that there are 36 amperes of continuous load, and 14 amperes of noncontinuous load. The minimum rating of the branch conductors is

59a

When not exposed to physical damage, a grounding electrode conductor can be run along the surface of the building. Additional protection of a grounding electrode conductor is not required provided the conductor size is:

6 AWG

Two resistors are connected in parallel, R1 has a value of 20 ohms and R2 has a value of 60 ohms. The current through R1 is:

6 amps Being a parallel circuit, all voltages are equal, ET = E1 = E2 = E3 Using ohms law: I1 = E1 / R1 = 120 volts / 20 ohms = 6 amperes

When two or more eight-foot ground rods are installed as part of the grounding electrode system, they shall be spaced by a distance of at least:

6 ft

When using the 75oC column of Table 310.16 and 240.4(B), a type MC cable with size 900 kcmil conductors can be protected by an overcurrent device up to, but not exceeding

600A

A termination of an electrical wire is a point where the wire is connected to a device, terminal screw or lug, or spliced with some type of splicing device such as a wire nut, split-bolt connector, or crimp connector. These terminations heat up when current is flowing, thus, they have a maximum temperature rating. Unless listed otherwise, the maximum temperature rating for a termination listed to accept a size 8 AWG copper wire with Type THHN insulation is:

60c

A termination of an electrical wire is a point where the wire is connected to a device, terminal screw or lug, or spliced with some type of splicing device such as a wire nut, split-bolt connector, or crimp connector. These terminations heat up when current is flowing, thus, they have a maximum temperature rating. Unless listed otherwise, the maximum temperature rating for a termination listed to accept a size 8 AWG copper wire with Type THHN insulation is:

60oC

Unless marked otherwise, the temperature rating of the terminations of a 100-ampere overcurrent device is:

60oC

An Enclosure Type that is suitable to be installed indoors or outdoors in a location that is subjected to prolong submersion under water is:

6P

The temperature rating of a type THHW conductor in a wet location is

75C

When installed in a wet location, the temperature rating of a type THWN conductor is:

75C

The maximum number of size 10 AWG conductors, or conductor equivalents that is permitted to be installed in a trade size 4 x 2-1/8 inch round/octagonal metal box is:

8

Assume that the total resistance of the circuit is 48 ohms, the current flowing through resistor R3 of the circuit is:

: 2.5 amperes. IT = ET / RTotal =120 V / 48 ohms = 2.5 amperes Being a circuit connected in series, all currents are equal, IT = I1 = I2 = I3

A grounding electrode conductor that is permitted by the Code to be either copper or aluminum. This grounding electrode conductor can be constructed of a:

All of the responses listed here are correct.

When type SE cable is used to supply electrical cooking units in newly constructed single-family dwellings, it is required to have a separate grounded neutral and equipment grounding conductor. The type of SE cable that has one red, one black, one white and one bare conductor within an outer jacket is style:

R

Equipment grounding conductor is the:

conductor used to connect non-current carrying parts of electrical equipment to the grounded conductor or the grounding electrodes.

NEC Section 250.104(B) requires the bonding of "other" metal piping systems. The Michigan Part 8 Electrical Rules has special rules for the bonding of corrugated stainless steel tubing (CSST) gas piping systems. Provided that the installation is in Michigan and the CSST gas piping system is not approved for bonding by the manufacture, a bonding jumper must be installed. The bonding jumper bonding this CSST gas piping system, must be:

connected to a metallic portion of the piping system between the gas meter and the first CSST fitting.

System grounding is the:

connection of a conductor, in an electrical system, to the earth, to limit the voltage imposed by lightning or line surges.

An Enclosure Type 3R is permitted to be installed outdoors and will not provide protection against:

corrosive agents.

A type NM 14-3, with ground, cable has the following conductors:

one bare, one white, one black and one red wire within the outer jacket.

A type SO flexible cord is marked as having conductors 14-3, the cord has the following conductors:

one green, one white and one black wire within the outer jacket.

An electrical circuit requires a:

source of power and a path for current to flow.

The color from the following list that is used to identify the grounded or neutral conductor is:

white

The cross-sectional area of a size 8 AWG type bare stranded conductor

0.017 in2.

From the following list, the electrical wire with the largest diameter is:

1/0 AWG

Where installed in a cable tray, conductors must be listed and marked for use in cable trays when the conductor are sizes:

1/0 AWG and larger

A transformer has the primary energized at 240 volts and the output is 120 volts. If there is 20 amperes flowing in the secondary circuit, the current flowing in the primary circuit will be:

10 amperes.

Unless attached with some means that require the use of tools to gain access inside a handhole enclosure, the cover must weigh at least:

100 pounds.

The rating of a 3-wire, 120/240-volt, single-phase service disconnecting means for a single-family dwelling shall not be less than:

100A

Three current-carrying conductors are installed in a raceway. The conductors are aluminum, type THWN, size 1/0 AWG. The allowable ampacity of the conductor is:

120 amperes.

A three-phase electrical motor draws 50-kW at 277 volts. The power factor is determined to be 0.84 and the efficiency of the motor is 0.90. The current flowing in any one of the three ungrounded conductors supplying the motor is approximately:

124.2 amperes

When using the 60oC column of Table 310.16 and 240.4(B), a size 1/0 AWG, copper, type TW conductor can be protected by an overcurrent device up to, but not exceeding

125A

According to Section 240.4(D), the maximum overcurrent protection device for a type MC cable where the conductors consist of a copper, AWG number 14 conductors is:

15A

A 14 foot length of rigid polyvinyl chloride conduit (PVC), Schedule 40 contains three size 2/0 AWG, type THW wires, six size 12 AWG, type THWN wires and one bare 6 AWG copper equipment grounding conductor. The minimum size of conduit permitted for this installation is:

2 inch.

The current drawn by a 250 watt incandescent infrared heat lamp operating at 120 volts is:

2.08 w/v=a

The volume allowance that is required for each size 10 AWG conductor, or conductor equivalent that is installed in a box is:

2.50 cubic inches.

If exposed to a 70oF change in temperature, a 100 foot run of rigid polyvinyl chloride (PVC) conduit will change in length:

2.84 inches.

A concrete-encased electrode must be encased by at least 2 inches of concrete and be located near the foundation or footing. It must be used as a grounding electrode if a connection is available and the metal rebars are at least 1/2 inch diameter and the effective length of the metal rebar is at least:

20 ft

The current flowing in the circuit where the circuit is energized at 120 volts and the resistance is 6 ohms is:

20A V/ohms=A

According to Section 240.4(D), overcurrent protection for a type THHN, copper, AWG number 12 conductor may not exceed:

20a

A resistance type heating element in a water heater is rated at 3500 watts and operates at 240 volts. The resistance of the heating element is:

16.46 ohms I = P/ E = 3500 watts / 240 volts = 14.6 amperes. R = E/I = 240 volts / 14.6 amperes = 16.4 amperes.

Under normal working conditions, the minimum value of current, for a human to perceive as an electrical sensation, is 1mA (1 milliampere). One milliampere is equal to:

0.001 A

The cross-sectional area of a size 8 AWG, type XHHW conductor is:

0.0437 in2.

A transformer has a secondary winding energized at 480 volts and the primary is 120 volts. The turns ratio of the transformer is:

1 to 4

A wire to a lamp is looped through the jaws of a clamp-around ammeter three times and the reading on the ammeter is 4.8 amperes. The actual current flow to the lamp is:

1.6 a ICircuit = Imeter / No. of Loops = 4.8 A / 3 Loops = 1.6 amperes

A 3-phase electrical service has a 400-ampere rated main circuit breaker and is supplied with size 750-kcmil, Type THWN aluminum service entrance conductors. The service entrance conductors are run in an intermediate metal conduit (IMC), which is secured to the service enclosure with a locknut on the inside and one on the outside. A bonding bushing on the inside of the conduit entry has a copper bonding wire run to the neutral terminal bus in the panelboard. The minimum size permitted for this copper supply-side bonding jumper is:

1/0 AWG

Examine the single-phase, 3-wire, 120/240 volt electrical system shown in the diagram. A 50 ampere load is connected between leg A and the neutral, a 40-ampere load is connected between leg B and the neutral. If a 240-volt load that draws 50 amperes is added to the system, the current flowing on the neutral conductor is:

10 amperes. Note, the solution to this question can be determined by two different methods. This method recognizes that no current of a 240-volt load is added to the neutral conductor. This method recognizes that the 240-volt load adds equal current to both leg A and leg B.

When using the 60oC column of Table 310.16 and 240.4(B), a size 1/0 AWG, aluminum, type TW conductor can be protected by an overcurrent device up to, but not exceeding

100 ampere

A load calculation for a branch circuit takes into consideration the requirements for continuous loads and noncontinuous loads and results in a total calculated load for the circuit of 12 amperes. The branch circuit conductors will be installed in a raceway. Also, the conductors will be protected with a 20-ampere rated circuit breaker and the conductors will be copper with Type THHN insulation. The minimum size conductors permitted for this circuit is

12 AWG.

A main feeder wire from the main service of a building to an electrical panel consists of two conductors which are 100 ft in length for a total of 200 ft of conductor. The total resistance for the 200 ft run of conductor is 0.015 ohms. If the current flow on the conductor is 160 amperes, the voltage drop for this feeder is:

2.40v

A dwelling is supplied with single-phase power at 120/240 volts, from a 3-wire electrical system with a single 150-ampere rated main circuit breaker. The calculated load for the building is 118 amperes. If the service entrance conductors are aluminum with Type THWN insulation, the minimum size permitted for this service is:

2/0 AWG

A pull box is installed, such that a 3 inch, trade size, electrical metallic tubing (EMT) enters one end of the box and leaves the opposite side of the box containing size 500 kcmil, Type THWN conductors. The minimum permitted distance within the pull box from one raceway entry to the other is:

24 inche

A transformer has 10 amperes flowing in the primary winding and 5 amperes flowing in the secondary winding. The primary winding operates at 120 volts. The voltage of the secondary winding is:

240 volts

The intersystem bonding termination must be accessible and have the capacity to terminate at least _______ intersystem bonding conductors.

3

Three incandescent lamps are connected in parallel with the first drawing 0.83 amperes, the second drawing 1.25 amperes and the third drawing 1.67 amperes. The reading on the clamp-around ammeter shown in the diagram will be approximately:

3.75 amperes. IT = 0.83 amperes + 1.25 amperes + 1.67 amperes

A given incandescent lamp draws 2.4 amperes, when connected to a 125 volt supply. The power drawn by the lamp will be:

300w VxA=W

A 100-ampere, single-phase service entrance is supplied with copper, size 4 AWG, service entrance conductors. If the only electrode available is a ground rod, the grounding electrode conductor is not required to be larger than a copper size:

8 AWG

A non-dwelling building is supplied with single-phase power at 120/240, 3-wire electrical system with a 400-ampere rated set of fuses in a single main disconnect. The calculated load for the building is 320 amperes. The service entrance conductors consist of two sets of parallel conductors run in separate raceways with not more than three current-carrying conductors in each raceway. The service entrance conductors are protected with rigid metal conduit (RMC). If the service entrance conductors are aluminum with Type THWN insulation, the minimum size permitted for this service is:

4/0 AWG

Unless listed otherwise, the maximum support spacing for vertically installed nonmetallic wireway is:

4ft

A standard rating of an overcurrent device, as recognized by the Code, is:

700A

A circuit with two resistors connected in series, has one with a value of 20 ohms ( R1 ) and the other with a value of 40 ohms ( R2 ). If the circuit is energized at 120 volts, the voltage across the 40-ohm resistor ( R2 ) is

80 volts. RT = 20 ohms + 40 ohms IT = ET / RTotal =120 V / 60 ohms = 2 amperes Being a circuit connected in series, all currents are equal, IT = I1 = I2 = I3 E2 = I2 x R2 = 2 A x 40 ohms = 80 volts

Eight current-carrying conductors are installed in a raceway. The conductors are aluminum, type THWN, size 1/0 AWG. The allowable ampacity of the conductors is:

84 amperes

Three current-carrying conductors are installed in a raceway. The conductors are aluminum, type THWN, size 1/0 AWG. The conductors are placed in an environment where the ambient temperature is 50oC. The allowable ampacity of the conductors is:

90 amperes.

The temperature rating of a type THHN conductor:

90C

A flexible cord that is rated for extra-hard usage is type:

SO

A dwelling is supplied power with a 120/240-volt, 3-wire, single-phase service. The water pipe entering the building is metallic and is used as a grounding electrode for the service. There is also a continuous section of twenty feet of reinforcement steel in the foundation that is made available to be used as a grounding electrode.

The reinforcing steel in the foundation is required to be used as a grounding electrode and is permitted to serve as the required supplemental ground for the metal water pipe.

From the list below, the item that is not considered a grounding electrode is:

a metal ungerground gas line

A panelboard that is used as service equipment is supplied by a 120/240-volt, three-phase, delta electrical system. The panelboard:

is to be field marked to indicate what phase conductor operates at a higher voltage-to-ground and what the voltage is to ground of that phase for the four-wire, three-phase, delta electrical system.

If an aluminum cable tray is to be used as an equipment grounding conductor for the circuit and feeder conductors that it supports, the cable tray shall be:

marked to show the cross-sectional area of the cable tray or side rails, which is sufficient for the circuit rating.

The main purpose of operating power transmission lines at high voltage is to:

minimize the current level needed to transport large quantities of electrical power.

A service entrance is grounded to a single eight-foot ground rod. The ground rod:

must be supplemented with one additional electrode, if the resistance of the ground rod is greater than 25 ohms.

Threaded couplings and raceway entries are suitable methods for bonding electrical equipment together for a service entrance. The Code requires these threaded connections be wrenchtight. The minimum number of threads that must be engaged are:

not specific in code

The service disconnecting means (not the emergency disconnected for one- and two-family dwellings) and main overcurrent protection, when located inside of a building is

required to be located as close as practical to the point where the service entrance conductors enter the building.

A bonding jumper is not permitted to be:

solder

When insulated conductors are installed in a location where they are exposed to direct sunlight, such as outdoors, they must be listed as being

sunlight resistant.

When a 120/240 volt, single-phase, three-wire electrical system is said to have the loads balanced:

the current on the middle (neutral or grounded) wire will be zero.

The underground water piping system entering a building is nonmetallic, but much of the interior water piping system is metallic. Even though this interior metal water piping system is not used as a grounding electrode, it is required to be bonded to the grounding electrode system of the building by connecting either directly to a grounding electrode, the grounding electrode conductor, or to a metal service enclosure or non-flexible metal service conductor raceway. If the service for a building consists of four parallel sets of service entrance conductors size 500 kcmil copper, the minimum size copper bonding jumper permitted to connect to this interior metal water piping system is:

250 kcmil

A branch circuit is installed in an agricultural facility. The circuit is protected by a 100-ampere fuse installed in a disconnect switch. The terminations (lugs) in the disconnect switch has a temperature rating of 75oC listed on it. The branch circuit consists of type SE cable that is installed on an exposed wall and the conductors are rated for 75oC. The minimum size of copper, type SE cable that is permitted to serve this load is a size:

3 AWG

A circuit supplies a 68-ampere continuous load in a barn. The circuit is protected by a 100-ampere fuse installed in a disconnect switch. The terminations (lugs) in the disconnect switch have a temperature rating of 75oC listed on them. The wires will be installed in a raceway, therefore, NEC Table 310.16 will be used. The minimum size of copper, type THW conductor that is permitted to serve this load is a size:

3 AWG

A circuit originates in a single-phase, 120/240 volt, 3-wire, circuit breaker panelboard from a 2-pole circuit breaker with two ungrounded conductors with 240 volts between the ungrounded conductors. There is a common neutral conductor with the two ungrounded conductors and these two 120-volt circuits supply lighting in a room. This type of circuit is known as

a multi-wire branch circut

An ac electrical system that is not required to be grounded is a:

240-volt, three-wire, three-phase delta system.

A load calculation for a feeder takes into consideration the requirements for continuous loads and noncontinuous loads and results in a total calculated load for the feeder of 155 amperes based upon the expected load to be supplied. The feeder conductors will be installed in a raceway, will be protected with a 200-ampere rated circuit breaker and the conductors will be aluminum with Type THWN insulation. The minimum size conductors permitted for this feeder is:

4/0 AWG.

A feeder in a building is protected with 1,000-ampere time-delay fuses and consists of three sets of parallel conductors run in separate raceways with not more than three current-carrying conductors in each raceway. If the conductors are copper with RHW insulation, the minimum size permitted for this feeder is:

400 kcmil

Alternating current means that:

electrical current flows back and forth in a conductor at a regular time interval.

Where a lightning protection system is installed, it shall be:

bonded to the grounding electrode system for the building or structure.