1b electrical
A balanced 3-wire, 120/240V, single-phase circuit is connected so that the ungrounded conductors are from different transformer phases (Line 1 and Line 2). The current on the neutral conductor is _____ percent of the ungrounded conductor current.
0
If the neutral of the circuit in the diagram is opened, the circuit becomes one series circuit of 240V. Under this condition, the current of the circuit is _____. Tip: Determine the total resistance. See Figure.
0.58A
What is the neutral current for a 4-wire, 120/208V circuit, where L1 = 20A, L2 = 20A, and L3 = 20A?
0A
A cable, raceway, or box installed under metal-corrugated sheet roof decking shall be supported so the top of the cable, raceway, or box is not less than _____ in. from the lowest surface of the roof decking to the top of the cable, raceway, or box.
1 1/2
A parallel circuit has three resistors. One resistor is rated 2 ohms, one is rated 3 ohms, and the other is rated 5 ohms. The total resistance of the parallel circuit is _____. Remember, the total resistance of any parallel circuit is always less than the smallest resistor.
1 ohm
The reading of Voltmeter 2 (V2) is _____. See Figure.
1.50V
Cables laid in wood notches require protection against nails or screws by using a steel plate at least _____ in. thick, installed before the building finish is applied.
1/16
An exposed wiring system for indoor wet locations where walls are frequently washed shall be mounted so that there is at least a _____ between the mounting surface and the electrical equipment.
1/4-in. airspace
Resistor R1 has a resistance of 5 ohms and resistors R2, R3, and R4 have a resistance of 15 ohms each. The total resistance of this series-parallel circuit is _____. See Figure.
10 ohms
The reading on Voltmeter 2 (V2) is _____. See Figure.
10V
Direct-buried service conductors that are not encased in concrete and that are buried 18 in. or more below grade shall have their location identified by a warning ribbon placed in the trench at least _____ in. above the underground installation.
12
What is the minimum cover requirement for Type UF cable supplying power to a 120V, 15A GFCI-protected circuit outdoors under a driveway of a one-family dwelling?
12 in.
Distribution transformers reduce the primary distribution voltage to secondary distribution voltage, such as _____.
120/208V 120/240V 277/480V Correct! any of these
The opening of the ungrounded or grounded conductor of a _____ circuit during the replacement of a device does not cause a safety hazard, so pigtailing of these conductors is not required.
2-wire
Determine the total circuit resistance of the parallel circuit shown in the Figure based on the following facts:1. The current on ammeter 1 reads 0.75A.2. The voltage of the circuit is 30V.3. Bell 2 has a resistance of 48 ohms.Tip: The total resistance of a parallel circuit is always less than the smallest resistor.
22 ohms
What is the voltage drop of each ungrounded conductor of a 4-wire multiwire circuit? Each conductor is 12 AWG, 100 ft in length, supplying a 16A load. The resistance of 12 AWG conductors is 2 ohms per 1,000 ft.
3.20V
The reading of V4 is _____. See Figure.
3V
Step-down substations reduce the voltage from the high-voltage transmission lines to a primary distribution voltage of _____.
4 kV to 35 kV
If Bell 2 consumes 12W of power when supplied by two 12V batteries (connected in series), the resistance of this bell is _____. See Figure.
48 ohms
Rigid metal conduit that is directly buried outdoors shall have at least _____ in. of cover.
6
What's the voltage drop across R1, if R1 is equal to 5 ohms and the total resistance of R2, R3, and R4 is 5 ohms? See Figure.
60V
A step-up substation located at the generating facilities transforms the 13.80 kV generator output to _____.
69 kV or higher
In the Figure, the total current of the circuit can be measured by ammeter _____.
A3
The total current of the circuit shown in the Figure can be read on _____.
Ammeter 1 Ammeter 2 Ammeter 3 all of these
_____ is defined as the area between the top of direct-burial cable and the top surface of the finished grade.
Cover
According to the equal resistance method, when all the resistances of the parallel circuit have the same resistance, divide the resistance of one element by the largest resistor in parallel.
False
In a parallel circuit, the total circuit resistance is always greater than the smallest resistance.
False
No matter how many resistances there are in a series circuit, the sum of the voltages across all of the resistances equals the voltage of the source according to the Law of Proportion.
False
The neutral conductor of a 4-wire, 120/208V or 277/480V, three-phase system has neutral current flow when the ungrounded conductors are equally loaded.
False
The power consumed in a series circuit is equal to the power consumed by the largest resistance in the series circuit.
False
There can never be variations in the formulas used or the order in which they are used for series circuits.
False
To prevent fires and electric shock, the NEC specifies that neutral current can flow on metal parts of the electrical system.
False
When installed under metal-corrugated sheet roof decking, the rules for spacing from roof decking apply equally to rigid metal conduit and intermediate metal conduit.
False
When power supplies are connected in series, the circuit voltage remains the same as when only one power supply is connected to it, provided that all the polarities are connected properly.
False
_____ breakers operate on the principle of electromagnetism only and are used for very large motors.
Instantaneous trip
_____ breakers operate on the principle that as the current increases, the time it takes for the device to open decreases.
Inverse time
A balanced multiwire branch circuit has current flow only on the ungrounded conductors.
True
A multiwire circuit has two or more ungrounded conductors having a potential difference between them, and having an equal difference of potential between each ungrounded conductor and the neutral conductor.
True
A parallel circuit has two or more paths in which current may flow.
True
According to Kirchoff's Current Law, the total current provided by the source to a parallel circuit equals the sum of the currents of all of the branches.
True
Electrons leaving a power supply are always trying to return to the same power supply; they are not trying to go into the earth.
True
If the ungrounded conductors of a multiwire circuit are not terminated to different phases, this can cause the neutral current to exceed the grounded conductor rating.
True
If you know the current of the circuit and the resistance of each resistor, the power of each resistor can be determined by the formula P = I2 x R.
True
In a parallel circuit, the voltage drop across each resistance is equal to the sum of the voltage drops of each of the resistors in parallel.
True
Kirchoff's Voltage Law states, "In a series circuit, the sum of the voltage drops across all of the resistors equals the applied voltage."
True
Resistance opposes the flow of electrons. In a series circuit, the total circuit resistance is equal to the sum of all of the resistances in series.
True
That portion of the series-parallel circuit that contains resistances in parallel must comply with the rules for parallel circuits.
True
That portion of the series-parallel circuit that contains resistances in series must comply with the rules for series circuits.
True
The advantage of the reciprocal method is that the formula can be used for as many resistances as the parallel circuit contains.
True
The current of the circuit can be determined by the formula I = ES/RT.
True
The grounded conductor is a conductor that is intentionally grounded to the earth.
True
The neutral conductor of a 3-wire, 120/240V, single-phase circuit only carries current when the current on the ungrounded conductors is not identical.
True
The opening time for a protection device is inversely proportional to the magnitude of the current. The greater the current value, the less time it takes for the protection device to open.
True
The opposition to current flow results in a voltage drop of the circuit voltage.
True
The total power consumed in a parallel circuit equals the sum of the power of all branches.
True
To calculate the total resistance of the circuit: RT = R1 + R2 + R3 +
True
To determine the resistance of each resistive element in the circuit, use the formula R = E2/P. E is the rated voltage of the resistor, and P is the rated power of the resistor.
True
When power supplies are connected in parallel, the voltage remains the same, but the current or amp-hour capacity will be increased.
True
When working with series-parallel circuits, it is best to redraw the circuit so you can see the series components and the parallel branches.
True
All conductors of the same circuit shall be _____, unless otherwise specifically permitted in the Code.
a or b in the same raceway or cable in close proximity in the same trench
Where exposed to sunlight, nonmetallic raceways, cable trays, boxes, cables with a nonmetallic outer jacket, fittings, and support hardware shall be _____.
a or b listed as sunlight resistant identified as sunlight resistant
Where Type NM cables pass through cut or drilled slots or holes in metal members, the cable shall be protected by _____ which are installed in the opening prior to the installation of the cable and which securely cover all metal edges.
a or blisted bushings listed grommets
As current flows through the element of a fuse, it generates heat. When a sustained overload occurs, the heat melts _____, stopping the flow of current.
a portion of the element
The electric utility grounds the primary and secondary neutral conductor to the earth at multiple locations for the purpose of reducing the _____ of the return current path.
ac resistance
Factors that impact the available short-circuit current include circuit conductor _____.
all of these
Cables or raceways installed using directional boring equipment shall be _____ for this purpose.
approved
Where corrosion protection is necessary for ferrous metal equipment and the conduit is threaded in the field, the threads shall be coated with a(n) _____ electrically conductive, corrosion-resistant compound.
approved
The voltmeters shown in the Figure are connected _____ each of the loads.
b and c
A 2-wire, 120V circuit, from a 2-wire 220V system, contains
b and c a grounded conductor ungrounded conductors
Type MC Cable listed for _____ is permitted to be installed underground under a building without installation in a raceway.
direct burial
Raceways or cable trays containing electric conductors shall not contain any pipe or tube for steam, water, air, gas, drainage, or any service other than _____.
electrical
Direct-buried conductors, cables, or raceways, which are subject to movement by settlement or frost, shall be arranged to prevent damage to the _____ or to equipment connected to the raceways.
enclosed conductors
Conductors of ac and dc circuits, rated 1,000V or less, shall be permitted to occupy the same _____ provided that all conductors have an insulation rating equal to the maximum voltage applied to any conductor.
enclosure cable raceway any of these
The total resistance of a parallel circuit can be calculated by the _____ method.
equal resistance product-over-sum reciprocal Correct! any of these
A 115/230V rated motor connected to a 230V circuit must have the windings connected in series so that each winding will receive at least 230V.
false
To remove dangerous touch voltage on metal parts from a(n) _____, the fault-current path must have low impedance to allow the fault current to quickly rise to facilitate the opening of the protection device.
ground fault
Spare or unused raceways shall be sealed with sealants _____ for use with the cable insulation, conductor insulation, bare conductor, shield, or other components.
identified
The most effective way to reduce conductor voltage drop and power loss is to lower the current flowing through the conductors. This is accomplished by _____ the transmission voltage.
increasing
A short circuit is a _____ electrical connection between any two conductors of the electrical system.
ine-to-line line-to-neutral a or b
The voltage drop over a conductor is directly proportional to the _____ of the conductor.
length
For locations not specifically identified in Table 300.5, a lesser cover depth than required in Column 5 shall be permitted where specified in the installation instructions of a(n) _____ low-voltage lighting system.
listed
Metal parts of the electric utility equipment are bonded to the utility neutral to provide a _____ path to the power source to assist in clearing a line-to-case fault.
low-impedance
Ferrous metal raceways, boxes, fittings, supports, and support hardware can be installed in concrete or in direct contact with the earth or other areas subject to severe corrosive influences, where _____ approved for the condition.
made of material
The purpose of overcurrent protection is to protect conductors and equipment against excessive or dangerous temperatures because of overcurrent. Overcurrent is current in excess of the rated current of equipment or conductors. It may result from a(n) _____.
overload
A single-phase, dual-rated, 120/240V motor will have its winding connected in _____ when supplied by 120V.
parallel
If the supply voltage is 120V, the total energy consumed for four 10-ohm resistors will be more if all of the resistors are connected in _____.
parallel
In general, when multiple light bulbs are wired in a single luminaire, they're connected in _____ to each other.
parallel
Because of the earth's high resistance to current flow, it cannot be used for the purpose of clearing a line-to-case ground fault for _____ wiring.
premises
All conductors of the same circuit, including the grounded and equipment grounding conductors and bonding conductors shall be contained within the same _____, unless otherwise permitted elsewhere in the Code.
raceway cable trench all of these
Where portions of a cable raceway or sleeve are subjected to different temperatures and condensation is known to be a problem, the _____ shall be filled with an approved material to prevent the circulation of warm air to a colder section of the raceway or sleeve.
raceway sleeve a or b
Backfill used for underground wiring shall not damage _____ or prevent adequate compaction of fill or contribute to corrosion.
raceways cables conductors all of these
A _____ is a circuit that contains some resistances in series and some resistances in parallel with each other.
series-parallel circuit
Series circuits are often used for _____ applications.
signal control a and b
A listed expansion/deflection fitting or other approved means shall be used where a raceway crosses a _____ intended for expansion, contraction or deflection used in buildings, bridges, parking garages, or other structures.
structural joint
Wiring methods installed behind panels that allow access shall be _____ according to their applicable articles.
supported
Kirchoff's Current Law states, "In a series circuit, the current is _____ through the transformer, the conductors, and the appliance."
the same
The _____ sensing element causes the circuit breaker to open when a predetermined calibration temperature is reached.
thermal
A series circuit is a circuit in which a specific amount of current leaves the voltage source and flows through every electrical device in a single path before it returns to the voltage source.
true
The product-over-sum method is used to calculate the resistance of _____ resistance(s) at a time.
two
The available short-circuit current is different at each point of the electrical system; it is highest at the _____.
utility transformer