4B Unit 4,5 test
What's the output watts of a 20 hp motor with an efficiency rating of 75 percent and a power factor of 70 percent?
15 Kw
What's the turns ratio of a transformer if the primary phase voltage is 480V and the secondary is 208V?
2.31:1
What size hp motor produces output power of 18kW?
25 HP
How many 16 TFFN conductors can be installed in trade size ¾ electrical metallic tubing?
29 conductors
How many 4/0 RHH conductors with an outer cover can be installed in trade size 2 IMC? Note: RHH insulation with an outer cover has no asterisk (*).
3 conductors
What's the minimum distance between the raceways of the angle pull?
15 in.
What's the minimum distance from the bottom wall to the top wall?
15 in.
What's the cross-sectional area of a 4 in. × 4 in. wireway?
16 sq in.
How many 14 AWG conductors can be pulled through a 4 in × 1% in, square box with a plaster ring marked 3.60 cu in 2 The box already contains two duplex receptacles, five 14 AWG conductors, and two grounding conductors.
2 conductors
The actual current drawn by a motor depends on the load placed on the shaft of the motor and the voltage at the motor terminals.
True
The transformer winding connected to the input power source is called the "primary." and the one connected to the load (output) is called the "secondary."
True
A transformer is designed to take electrical power input at a certain voltage and, using _______, create electrical power output at the desired voltage.
Electromagnetic induction
The output mechanical work of a motor is rated in ______.
Horsepower
The counter-electromotive force (CEMF) in a motor opposes the applied voltage resulting in an increased opposition to current flow through the wire. This is called "________"
Inductive reactance
Where the primary and secondary windings of a transformer both have the same number of turns, the secondary will deliver the same voltage as the primary and is called a(n) "_____ transformer."
Isolation
What's the turns ratio of a transformer if the primary winding voltage (Ep) is 240V and the secondary winding voltage (Es)
4:1
How many 6 THW-2 compact conductors can be installed in trade size 1 EMT?
5 conductors
What's the minimum size wireway required for six 500 kcmil THHN conductors?
6 in.
When a raceway doesn't exceed 24 in. in length, the raceway is _______ permitted to be filled to percent of its cross-sectional area.
60
What's the motor nameplate full-load amperes (FLA) for a 15 hp, 230V, single-phase motor having an efficiency rating of 93 percent and a power factor of 87 percent?
60 A
How many 1/0XHHW conductors can be installed in trade size 2 flexible metal conduit?
7 conductors
The conversion of mechanical work to electrical energy is measured in watts where one horsepower = ______ watts.
746 W
How many 10 AWG conductors are permitted in a 4 in. square × 1½ in. deep box?
8 conductors
What's the primary and secondary line current at full load for a 480/240V, 75 kVA, three-phase transformer?
90/180 A
When conductors 4 AWG and larger are installed in boxes and conduit bodies, the enclosure must be sized according to which of the following requirements?
All of these
Transformer power losses are a result of ______ and hysteresis losses
All of these wire resistance flux leakage eddy currents
When all the conductors are the same size (total cross-sectional area including insulation), the number of conductors permitted in.
Annex C
When voltage is first applied to the field winding of an inducution motor, the motor has a very large inrush current.
True
What's the secondary voltage of a transformer if the turns ratio is 4:1 and the primary voltage is 480V?
120 V.
What's the minimum distance from the left wall to the right wall?
14 in
What's the minimum distance from the left wall to the right wall?
20 in
HoW many 18 TF conductors can be installed in trade size ¾ electrical metallic tubing?
24 conductors
When determining the number of conductors for box fill calculations, which of the following statements is (are) true?
All of these
When determining the number of conductors for box fill calculations, which of the following statements is(are) true?
All of these
What's the primary voltage of a transformer if the turns ratio is 30:1 and the secondary voltage is 240V?
7,200 A
A 120V transformer for a doorbell requiring only 16V has a turns ratio of _______.
7.50:1
There are multiple directions in which voltage can be transformed. It can be stepped up, stepped down, or left the same.
True
Can a round 4 in. x ½ in. box marked as 8 cu in. with cable clamps supplied with 14/2 W/G NM cable be used with a luminaire that has two 18 TFN conductors and a canopy cover?
Yes
identify(ies) the current in amperes that a motor circuit will carry during different types of operation.
All of these Full-oad current (FLC) Full-oad amperes (FLA) Locked-rotor amperes/current (LRA/LRC)
The number of conductors permitted in a raceway is dependent on the ________.
All of these area of the raceway percent of area fill as listed in Chaptr 9Table 1 area of the conductors as listed in Chapter 9, Tables 5 and 8
The stationary field winding of a motor is mounted on the ______.
Stator
What trade size ENT is required for four fiber optic cables having a diameter of .30 inches.
Trade size 1
A transformer consists of _______ wire windings that are electrically insulated from each other.
Two
Dual-voltage alternating-current motors are made with ________ winding(s).
Two
Once the motor's rotor begins turning, the rotor windings are increasingly cut by the stationary magnetic field, resulting in an increasing ______ in the wire windings.
counter-electromotive force (CEMF)
What's the cross:-sectional area in square inches for a 10 THW conductor?
0.0243 sq in.
What's the secondary wire power loss of a 112.50 kVA transformer if the secondary current rating is 135A and the winding has a resistance of 0.16 ohms?
2,916 W
What's the maximum allowable sq in. of conductor fill for a 4 in. × 4 in. wireway?
3.2 sq in.
What's the smallest trade size PVC Schedule 40 raceway that can be used for the installation of four 1/0 THHN conductors?
Trade size 1 1/2
A 200A feeder installed in Schedule 80 PVC has three 3/0 THHN conductors, one 2 THHN conductor, and one 6 THHN conductor. What size raceway is required?
Trade size 2 raceway
What trade size ENT raceway is required for four Cat 6 cables having a diameter of 0.22 inches?
Trade size 3/4
What's the minimum trade size EMT required for Type NM cable having a major diameter (ellipse) of 0.50 in.?
Trade size 3/4
A motor is a machine that converts electrical energy into mechanical energy.
True
Autotransformers use a single winding for both the primary and secondary and are often referred to as "buck-boost transformers."
True
Circuit breakers and fuses typically provide short-circuit and ground -fault protection, while overload protection is provided separately in the form of overload devices such as bimetal heaters or electronic sensors.
True
Delta/delta- and delta/wye-connected transformers are made up of three single-phase transformers.
True
Each time a transformer's primary electromagnetic field expands and collapses, the iron or steel core's bonded electrons realign themselves to the changing polarity of the electromagnetic field.
True
For a motor to rotate, it must have two opposing magnetic fields: one magnetic field on the stator (stationary field winding) and the other one on the rotor (rotating field winding).
True
If a motor is overloaded, or if it operates at a voltage below 90 percent of its nameplate voltage rating, the operating current can increase to a value above the motor's nameplate full-load ampere (FLA) rating.
True
If there are 10 turns of wire in the primary and 5 turns of wire in the secondary. then there are two turns of wire on the primary side for every turn of wire on the secondary. This is referred to as a two to one ratio transformer and is written as "2:1."
True
Iron or steel core losses are responsible for heating in a transformer and contribute to the heating of windings.
True
The expanding and collapsing electromagnetic field from alternating current within iron or steel cores of transformer windings induces a voltage which creates wasteful circulating
Eddy current
Transformers can't transfer all the electromagnetic flux from the primary to the secondary. The flux that's lost during the transfer is called " _________"
Flux leakage
It's permitted to omit one equipment grounding conductor and not more than ______ 18 AWG or 16 AWG fixture wire(s) that enter a box from a luminaire canopy.
Four
The transfer of energy from the primary winding to the secondary winding of a transformer is accomplished because the electro-magnetic lines of force from the primary winding induce a voltage in the secondary winding. This process is called "__________"
Mutual induction
The rotating part of a motor is referred to as the "rotor" and contains the rotating field winding whose electromagnetic field opposes the electromagnetic field of the stator's windings.
True
The voltage of the secondary winding of a transformer is equal to the sum of the voltages induced in each loop (turn) of the secondary winding.
True
Transformer losses are typically quite small with efficiencies approaching 97 percent. For most practical purposes, transformer efficiency can be ignored when performing transformer calculations.
True
Transformers are rated in kilovolt-amperes (kVA); common standard transformer sizes used in commercial/industrial applications typically run between 3 kVA and 2.500 kVA.
True
When equipment grounding conductors are installed in a raceway, the actual area of the conductor must be used when calculating raceway fill.
True
Wire resistance in a transformer is directly proportional to its length and inversely proportional to its cross-sectional area.
True
The relationship between the number of wire turns (loops) between the primary and secondary windings of a transformer is called the "_________"
Turn ratio
Common types of motor overload protection are the type and solid-state or electronic type overload relays.
All of these melting alloy dashpot bimetallic
What's the cross-sectional area in square inches for an 8 AWG bare solid conductor?
0.013 sq in.
What's the cross-sectional area in square inches for a 14 RHW conductor (without an outer cover)?
0.0209 sq in.
What's the cross-sectional area in square inches for a 10 THHN conductor?
0.0211 sq in.
What's the cross-sectional area in square inches for a 12 RHH conductor (with an outer cover)?
0.0353 sq in.
What size box is the minimum required for six 14 THHN conductors and three 14 THW conductors?
4 in. x1¼ in square box
The motor nameplate full-oad ampere (FLA) rating is deter- mined by the factory, but it can also be calculated.
True
An existing trade size ¾ rigid metal conduit that doesn't exceed 24 in. in length contains four 10 THHN conductors and one 10 AWG (bare stranded) ground wire. How many 10 THHN conductors can be installed?
11 conductors
How man 12 RHH conductors (with outer cover) can be installed in a trade size 1 IMC racewav?
11 conductors
What's the maximum number of 400 kcmil THHN conductors that can be installed in a 6 in. × 6 in. wireway?
12 conductors
Three THHN compact conductors are needed in a trade size 2 rigid metal conduit. What's the largest compact conductor that can be installed?
350 kcmil
What size outlet box is required for one 12/2 W/G NM cable that terminates on a switch and one 12/3 W/G NM cable that terminates on a receptacle? The box has cable clamps.
4 in. × 2⅛ in. square box
The actual area of conductor fill is dependent on the raceway size and the number of conductors installed. If there are three or more conductors installed in a raceway, the total area of conductor fill is limited to _______ percent.
40
What's the transformer primary line current (Ipep) and secondary line current (sEc) at full load for a 240/120V, 10 kVA transformer?
42/84 A
The National Electrical Code provides requirements, in Article _________, for sizing overload devices to protect motors based on the motors' full-load amperes (FLA).
430
What's the motor nameplate full-load amperes (FLA) for a 50 hp, 480V, three-phase motor having an efficiency rating of 80 percent and a power factor of 90 percent?
70 A
What's the primary wire power loss of a 50 kVA transformer if the primary current rating is 60A and the winding has a resistance of 0.22 ohms?
792 W
How many 6 RHH conductors (without outer cover) can be installed in trade size 1¼ electrical nonmetallic tubing?
8 conductors
Table 314.16(A) doesn't take into consideration the volume ________.
All of these. switches and receptacles luminaire studs and hickeys internal cable clamps
According to Annex C, Table C.1, three 3/0 THHN conductors can be installed in 1½ EMT. Will this installation have the possibility of jamming?
No
When conductors enter an enclosure opposite a removable cover, the distance from where the conductors enter to the removable cover must not be less than _____ times the largest
None of these
Locked -rotor current (LRC) is also called locked-rotor amperes (LRA) and is the current drawn by the motor when power is applied to the motor and its shaft (rotor) is prevented from rotating.
True
What trade size rigid metal conduit is required for three 4/0 THHN conductors, one 1/0 THHN conductor, and one 4 THHN conductor when the raceway is 24 in. or less in length?
Trade size 1 1/2
What trade size ENT is required for three fiber optic cables having a diameter of 0.20 inches?
Trade size 1/2
It takes more than 746W of input energy to produce one horse- power of mechanical work because energy is lost between the input power of a motor and the output mechanical force.
True
The amount of energy transferred between the primary and secondary windings of a transformer is proportional to the number of turns of wires on the primary winding compared to the number on the secondary winding.
True
The motor full oar amperes rating is the nameplate rating of the motor and is ine carrent in amperes the motor draws while producing its rated horsepower at its rated voltage.
True
The motor full-oad current rating is the current as listed in the NEC Article 430 Tables and is used to size motor wires and short-circuit and ground-fault protection.
True
