Quarter 1 Year 3 Exam
The neutral conductor of a 4-wire, 120/208V or 277/480V circuit that supplies linear loads only carries the unbalanced phase current. If the current on all three phases is the same, then the neutral current is _____.
0A
Three-phase power consists of three waveforms which are out-of-phase with each other by _____ degrees.
120
If an excavation is four ft deep or greater, an exit must be provided within _____ ft of every worker.
25
OSHA considers an unattended vehicle to be _____ ft away from the operator.
25
When driving fasteners into materials like brick or concrete, they should never come any close than _____ in. to an edge or corner.
3
Phase differences are often expressed in degrees; one full waveform is equal to _____ degrees.
360
Single-phase nonlinear loads produce odd harmonics. Current which are multiples of the 3rd harmonic, are called "triplen" harmonics, for instance the _____.
3rd, 9th, and 15th (all of these)
The NEC recommends no more than a _____ percent voltage drop of nominal system voltage for feeders and branch circuits
5
In common electrical distribution systems in the United States, the fundamental frequency is _____ Hz.
60
The class of hard hat that provides no voltage protection is _____.
Class C
When driving a motor vehicle on a jobsite, you should abide by _____.
OSHA rules, company rules, good common sense rules ( all of these)
The relationship between voltage (E), current (I), and resistance (R) can be demonstrated via _____ Law.
Ohm's
_____ are prohibited from being installed in the same raceway, cable, cable tray, outlet box, or similar enclosure with power or lighting conductors.
Remote-signaling circuits, Power-limited fire alarm circuits, Optical fiber cables (all of these)
_____ is an example of a linear load.
Resistance heating and incandescent lighting (a and b)
Understanding how electricity works requires knowledge of _____.
Volts = Current x Resistance
A dump truck must have additional equipment above and beyond regular vehicles, which includes _____.
a cab shield
Hazards that can cause electrical injuries include _____.
a cracked extension cord
For the flow of energy to occur, you need a combination of _____.
a generating source, conductor, and load keyboard_backspace selected,: electricity, wiring, and equipment, a voltage source, electron flow, and a consuming device, (all of these)
OSHA requires emergency rescue equipment when _____.
a hazardous atmosphere may reasonably develop
If the view to the rear is obstructed, a motor vehicle operator must not operate it unless _____.
a reverse signal alarm can be heard above noise levels or an observer says it's safe to back up ( b and c)
There are many different makes and styles of respirators, but all of them fall into two types which are _____.
air-purifying respirators and atmosphere-supplying respirators
A simple _____ consists of a loop of wire rotating between the lines of force between the opposite poles of a magnet.
alternating-current generator
Excavations are _____.
any man-made depression into the earth's surface by earth removal
The hazard(s) faced while working in and around an excavation include(s)
asphyxiation, electrocution, or cave-ins (all of these)
When using a saw, knife, or other tools direct them _____ other employees working nearby.
away from
_____ are electrical devices that store energy in an electric field between closely spaced plates and are capable of releasing the energy at a later time.
capacitors
Gasoline-powered motor vehicles emit deadly _____ into the air.
carbon monoxide
A general safety rule to keep in mind when working with tools is to _____.
choose the right tool for the job
An example of Type A soil is _____.
clay
To reduce electromagnetic interference (noise), avoid installing _____ conductors near power equipment.
communications, control, and signaling (all of these)
The hazard(s) faced on a jobsite that could cause foot injuries include(s) _____.
compression
The type of foot protection that should be used to prevent the accumulation of static electricity is _____.
conductive shoes and static dissipative shoes (a and b)
The Assured Equipment Grounding Conductor Program requires the following test(s) to be conducted before first use of new equipment: _____.
continuity test, grounding conductor test, and visual inspection ( all of these)
In the process of removing or avoiding hazards, you must recognize the _____.
dangers associated with different types of tools, safety precautions necessary, hazards of power sources (all of these)
A hand-held powered tool that must be equipped with a momentary contact "on-off" control switch is a _____.
drill
The type(s) of materials that can cause eye injuries include(s) _____.
dust, metals, and vapors (all of these)
According to the _____ theory, electrons flow away from the negative terminal of the source, through the circuit and load, toward the positive terminal of the source.
electron current flow
A "nonlinear load" is one that opposes the applied voltage with constant impedance, resulting in a current waveform that changes in direct proportion to the sinusoidal change in the applied voltage.
false
Passive inductive-capacitive series LC harmonic filters tuned to the offending harmonic and connected in series to the load, are used to reduce reflective harmonic currents.
false
Never operate a vehicle that is missing _____.
fenders or mud flaps
The Department of Transportation has identified Class 3 materials as _____.
flammables or combustibles
Voltage _____ can occur when nonlinear loads switch on and off near the peak of the voltage waveform.
flat-topping
Machine guards protect operators from _____.
flying chips and sparks
The harmonic order is simply the ratio of the _____ of the harmonic to the fundamental frequency.
frequency
The type of eye protection that should be used to guard against dust particles is _____.
goggles
Arcing occurs when _____.
high-amperage current jumps through air, circuits are opening or closing, static electricity is discharged (all of these)
A hard hat should be worn in working areas where there is a possible danger of head injury from _____.
impact, electrical shock or burns, or falling or flying objects (all of these)
Shock can result when your body is _____.
in contact with two wires of an electric circuit
As frequency _____, XL increases and XC decreases. At a certain frequency they can reach an equal value, and at this point they are said to be in resonance.
increases
Proper lockout/tagout of electrically-powered equipment includes _____.
indicating circuits or pieces of equipment are out-of-service on tag
To prevent electrical accidents _____.
insulate
All conductors must terminate in devices that have been properly tightened in accordance with _____ torque specifications included with equipment
manufacturer's
The 4-foot rule means a(n) _____.
means of egress must be provided at 4 ft
The type(s) of hand hazards that you can be exposed to on a job site include(s) _____.
mechanical, environmental, and chemical (all of these)
If required to wear a respirator, you must first have a _____.
medical evaluation
A _____ consists of two or more ungrounded conductors having a potential difference between them, and having an equal potential difference between each ungrounded conductor and the neutral conductor.
multiwire circuit
The electrical term "_____" refers to the common point on a wye connection in a polyphase system or the midpoint on a single-phase portion of a three-phase delta system, or the midpoint of a 3-wire, single-phase system.
neutral point
While working in excavations, you should know that _____.
no work must occur if there's water accumulation unless precautions are taken
A "nonlinear load" is one that does not oppose the applied voltage with constant impedance. This results in a _____-current waveform.
nonsinusoidal
Silicon Controlled Rectifiers (SCR) used for three-phase motor variable speed drives, large UPS systems, or induction heating equipment can cause "_____" in the voltage waveform.
notches
A conductor of electricity includes _____.
perspiration
Tools that are powered by compressed air are known as _____ tools.
pneumatic
Electrical current flows from the power source through the load and then it returns to the ______. This path is called the "electrical circuit."
power source
Before an excavation can begin, a competent person must _____.
remove or secure surface obstacles and classify the type of soil and rock deposits (b and c)
A capacitor can be thought of as a device that _____ changes in current.
resists
_____ is occurs when inductive reactance and capacitive reactance are equal (XL = XC).
resonance
The combination of the fundamental 60 Hz and reflective harmonic currents produce a nonsinusoidal _____ or complex current waveform.
resultant
Before an abrasive wheel is mounted, it shoud be _____ tested.
ring
The type of hand protection that should be used to prevent exposure to caustic chemicals is _____ gloves.
rubber, vinyl, or neoprene
"Voltage _____" is a short duration decrease in voltage caused by a short duration increase in current flow, such as a motor starting.
sag
Alternating-current flow in a conductor is limited by the conductor's resistance and _____ (CEMF).
self-induced voltage
The type(s) of protective system(s) that can protect from cave-ins include(s) _____
shielding and shoring (b and c)
Always perform a pre-operational inspection of the motor vehicle at the beginning of each _____.
shift
For most alternating-current circuits, the waveform is called a "_____."
sine wave or sinusoidal waveform (a or b)
_____ voltage is produced at the source, but it is often degraded because of load variations that distort the voltage waveform.
sinusoidal
_____ protect equipment by preventing damaging transient voltage surge levels from reaching the devices they protect.
surge protection devices (SPDs)
The two types of grounding are _____.
the electrical circuit and electrical equipment
"_____" is defined as the ratio of the harmonic voltage or current components to the fundamental; expressed as a percent.
total harmonic distortion
A competent person is _____.
trained and capable of identifying hazards, responsible for inspecting excavation and adjacent areas, given the authority to take prompt corrective measures (all of these)
_____ (sometimes called voltage spikes) caused by the switching of utility power lines or power factor correction capacitors, or lightning can reach thousands of volts and amperes.
transients
A "linear load" is one that opposes the applied voltage with constant impedance.
true
Electrons only flow when there is relative motion between the conductor and the magnetic field.
true
Failure to torque terminals is a violation of NEC 110.3(B), which requires all equipment to be installed in accordance with listed or labeling instructions.
true
Frequency is expressed as cycles per second, or Hertz (Hz).
true
If a vehicle is not in compliance with OSHA and manufacturer standards, you should tag, lock, or physically remove it from the jobsite.
true
In a series LC circuit, as the frequency approaches the resonance frequency, the impedance of the LC circuit decreases so that the only opposition to current flow will be the conductor resistance.
true
In generators that produce large quantities of electricity, the conductor coils are stationary and the magnetic field revolves within the coils.
true
Self-induced voltage (CEMF) acts to oppose the change in current flowing in the conductor.
true
Shielding of cables does not significantly reduce the noise caused by harmonic currents.
true
The Information Technology Industry Council provides recommendations to their membership regarding the proper system operating voltage window.
true
The National Electrical Code does not limit conductor voltage drop for most feeders and branch circuits.
true
When nonlinear loads are supplied from 4-wire wye circuits, odd multiples of 3rd order harmonic currents do not cancel, but instead, add together in the neutral conductor.
true
The current flowing on the neutral conductor of a three-wire, single-phase circuit will be the difference between the current flowing on the ungrounded conductors, and is often referred to as the _____.
unbalanced current
Because the neutral conductor can be overloaded by _____ currents, it is critical that the neutral conductor be sized properly.
unbalanced neutral and additive triplen harmonic (a and b)
A voltage sag lasting more than three seconds is classified as a(n) _____ condition.
undervoltage
When entering or exiting a motor vehicle, you should _____.
use anti-slip surfaces
An example of hand tool misuse is _____.
using a chisel to tighten a screw
The most serious hazard with fuel-powered tools comes from _____.
vapor
Harmonic currents are produced when electronic loads change their impedance so the waveform of the current does not look like the _____ waveform.
voltage
The _____ of a circuit is distributed across all components of the circuit, such as the power supply, circuit conductors, load, and loose terminations, in proportion to their resistance to the entire circuit resistance.
voltage
