Electrical 2A Final Exam Review.

Where exposed to the weather, raceways enclosing service-entrance conductors shall be _____ for use in wet locations and arranged to drain.

(a) approved (b) listed.

What's the direct-current resistance of a 1 AWG copper conductor that's 100 ft long?

0.0154 ohms.

What's the alternating-current ohms-to-neutral resistance for a 2/0 AWG copper conductor that's 300 ft long?

0.03 ohms.

What's the direct-current resistance of a 1 AWG copper conductor that's 200 ft long?

0.0308 ohms

What's the direct-current resistance of a 3 AWG aluminum conductor that's 500 ft long?

0.2015 ohms.

What's the direct-current resistance of a 3 AWG aluminum conductor that's 1,000 ft long?

0.403 ohms.

What's the feeder or service demand load for a disposal (waste) (940 VA), a dishwasher (1,250 VA), and a water heater (4,500 W)?

6,690 VA

If the branch-circuit supply voltage is 208V, the maximum recommended voltage drop of the circuit shouldn't be more than _____.

6.24V.

What's the ampacity of an 8 THHN conductor when installed in a walk-in cooler (dry location) if the ambient temperature is 50°F?

63A.

Cable tray systems shall not have mechanically discontinuous segments between cable tray runs or between cable tray runs and equipment.

False

The unit of inductance is the _____.

Henry (H).

A pure direct-current waveform displays the polarity and magnitude of the current or voltage as a flat waveform.

True.

The symbol for reactance is _____.

XL.

Phase differences are expressed in _____.

degrees.

A charge curve for a capacitor is divided into _____ time constants.

five.

Horizontal runs of RMC supported by openings through _____ at intervals not exceeding 10 ft and securely fastened within 3 ft of termination points shall be permitted.

framing members.

Each direct-buried single conductor cable shall be located _____ in the trench to the other single conductor cables in the same parallel set of conductors, including equipment grounding conductors.

in close proximity.

The movement of electrons caused by an external magnetic field is called "_____ current," and the associated potential that is established is called "_____ voltage."

induced.

A nonsinusoidal waveform is created when _____ loads distort the voltage and current sine wave.

nonlinear.

If a capacitor is overcharged, the electrons from the negative plate can be pulled through the insulation to the positive plate. The capacitor is said to have _____.

shorted.

When describing the relationship between voltage and current waveforms, the reference waveform (the one used to compare against) is the _____.

voltage.

Power is the rate at which electrical energy is transferred by an electric circuit in a given amount of time at a steady rate and is measured in _____.

watts.

Conductors, splices, or terminations in a handhole enclosure shall be listed as suitable for _____.

wet locations.

Type MC cable provides an effective ground-fault current path and is recognized by the NEC as an equipment grounding conductor _____.

when it contains an insulated or uninsulated equipment grounding conductor in compliance with 250.118(1).

Each dwelling unit must have a load of _____ for the 20A laundry circuit.

1,500 VA.

Type MC cable containing four or fewer conductors, sized no larger than 10 AWG, shall be secured within _____ in. of every box, cabinet, fitting, or other cable termination.

12.

What size feeder conductor will be required for a feeder supplying a 100A continuous and a 100A noncontinuous load?

4/0 AWG.

How many 20A, 120V circuits are required for forty-two, 300W incandescent luminaires (noncontinuous load)?

6 circuits.

If the input power of a 1 hp dc motor is 1,128W and the output power is 746W, what is the efficiency of the motor?

66%.

The resistance of a conductor is directly proportional to its length.

True.

Where practicable, rod, pipe, and plate electrodes shall be installed _____.

below permanent moisture level.

Nonpolarized capacitors _____.

can be used with either AC or DC.

In order to induce voltage, relative motion is required between a conductor and a _____ field. This is the basis of the generator and transformer.

magnetic.

Volt-amperes-reactive is used to measure the _____ in a pure inductive circuit.

reactive power.

Factors that determine the capacitance of a capacitor are the _____ the plates.

surface area of. distance between. dielectric between.

What size conductor should be used to limit voltage drop from exceeding three percent if the equipment nameplate indicates an 18A continuous load at 480V, three-phase and it's located 300 ft from the power supply?

10 AWG.

Nonmetallic-sheathed cables can enter the top of surface-mounted cabinets, cutout boxes, and meter socket enclosures through nonflexible raceways not less than 18 in. and not more than _____ in length if all of the required conditions are met.

10 ft.

Overhead service conductors shall have a minimum vertical clearance of _____ ft from final grade over residential property and driveways, as well as over commercial areas not subject to truck traffic where the voltage does not exceed 300 volts-to-ground.

12ft.

What's the total connected load for lighting and general-use receptacles, and small-appliance and laundry circuits for a 6,540 sq ft dwelling unit?

24,120 VA.

What's the ampacity of 10 THHN conductors when there are eight current-carrying conductors installed in the same raceway in a dry location and the ambient temperature is 100°F?

25A.

Each dwelling unit must have a load of _____ for the small-appliance circuits.

3,000 VA.

What size overcurrent protection will be required for a branch circuit supplying a 32A continuous nonlinear load?

40A.

The total rating of utilization equipment fastened in place, other than luminaires, shall not exceed _____ percent of a multiple outlet branch circuit rating.

50.

Securing or supporting of LFNC is not required where installed in lengths not exceeding _____ from the last point where the raceway is securely fastened for connections within an accessible ceiling to a luminaire(s) or other equipment.

6 ft

If the feeder supply voltage is 240V, the maximum recommended voltage drop of the feeder shouldn't be more than _____.

7.20V.

Conductors shall have their ampacity determined using the _____ column of Table 310.16 for circuits rated over 100A, or marked for conductors larger than 1 AWG, unless the equipment terminals are listed for use with higher temperature-rated conductors.

75.

Where six current-carrying conductors are run in the same conduit or cable, the ampacity of each conductor shall be lowered to _____ percent of its ampacity.

80%.

A three-phase generator has each of its three windings evenly spaced around the rotor and the windings are 120° out-of-phase from each other.

True.

Alternating-current circuits of less than 50V shall be grounded if supplied by a transformer whose supply system exceeds 150 volts-to-ground.

True.

Because an iron core provides an easy path for magnetic flux, windings with soft iron cores produce a greater self-inductance than windings with air cores.

True.

Capacitors are used to start single-phase ac motors and to prevent arcing across the contacts of electric switches.

True.

To determine the true power consumed by a dc circuit, multiply the volts by the amperes.

True.

When a _____ has reached its maximum potential difference between its metal plates, it's said to be "charged."

capacitor.

Conductor overload protection shall not be required where the interruption of the _____ would create a hazard, such as in a material-handling magnet circuit or fire pump circuit. However, short-circuit protection is required.

circuit.

The opposition to current flow is greater for alternating-current circuits than for direct-current circuits because of _____.

eddy currents. skin effect. inductive reactance.

For ac circuits, the ac _____ of a conductor must be taken into consideration.

eddy currents. skin effect. resistance.

A(n) ______ shall be used to connect the grounding terminal of a grounding-type receptacle to a grounded box.

equipment bonding jumper.

In a purely resistive ac circuit, the current and voltage are _____. This means that they both reach their zero and peak values at the same time.

in-phase.

A capacitor can be thought of as a device that resists changes in current. Because a capacitor introduces reactance to the circuit, it shifts the current waveform to _____.

lead the applied voltage by 90°.

The output voltage of a generator depends upon the _____.

number of turns of wire strength of the magnetic field speed at which the coil rotates

When an ac circuit supplies power to a purely _____ load, the circuit voltage and current will be in-phase with each other. This condition is called "unity power factor."

resistive.

Eddy currents are small independent currents near the center of a wire that are a result of _____ from the expanding and collapsing electromagnetic field.

self-induction.

THHN can be described as _____.

thermoplastic insulation with a nylon outer cover having a maximum operating temperature of 90°C.

When a wire is coiled into adjacent loops (helically wound), it's called a(an) _____.

winding.

If the circuit's overcurrent device exceeds _____, the conductor ampacity shall have a rating not less than the rating of the overcurrent device.

800A.

According to Chapter 9, Table 8, what's the cross-sectional area in circular mils for a 1 AWG conductor?

83,690 cmil.

A 240V, 24A, single-phase load is located 160 ft from the panelboard. The load is wired with 10 AWG conductors. What's the approximate voltage drop of the branch-circuit conductors?

9.50V.

An inductor is connected to a 120-V, 60-Hz supply. The current in the circuit is 2.4 A. What is the inductive reactance?

904.8 Ω.

A waveform image is used to display the level and direction of current, but not voltage.

False.

AC inductive or capacitive reactive loads cause the voltage and current to be in-phase with each other.

False.

Conductor resistance is directly proportional to the conductor's length and cross-sectional area.

False.

The ampacities listed in Table 310.16 apply only when the ambient temperature is 40°C and there are no more than two current-carrying conductors bundled together. If the ambient temperature isn't 40°C, or there are more than two current-carrying conductors in a raceway, the allowable ampacities must be corrected and/or adjusted to reflect the ampacity under the conditions of use.

False.

The number of complete waveforms in one second is called the "frequency." Frequency is expressed as "_____" or "cycles per second.

Hertz.

How can conductor voltage drop be reduced?

Increase the supply voltage. Increase the conductor size. Decrease the conductor length.

"_____" is the value of the voltage or current at a moment of time.

Instantaneous.

Raceways shall be provided with expansion, expansion-deflection, or deflection fittings where necessary to compensate for thermal expansion, deflection, and contraction.

True.

The 3 VA for each square foot of living space for general lighting includes receptacles rated 15A and 20A, but not the small-appliance or laundry circuit receptacles.

True.

The Power Formula Circle ("Watt's Law") demonstrates the relationship between power, current, and voltage. Watt's Law states that power is equal to current x voltage.

True.

The intensity of a magnetic field depends on the intensity of alternating current. The greater the current flow, the greater the overall magnetic field.

True.

The maximum overcurrent protective device size for 14 AWG is 15A, 12 AWG is 20A, and 10 AWG is 30A. This is a general rule, but it doesn't apply to motor or air conditioner loads according to 240.4(G).

True.

The movement of electrons themselves does not produce any useful work. It's the effects that the moving electrons have on the loads they flow through that are important.

True.

Where a branch circuit supplies continuous loads, or any combination of continuous and noncontinuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load.

True.

Where conductors in parallel are run in separate raceways, the raceways shall have the same electrical characteristics.

True.

The opposition offered to the flow of alternating current by a capacitor is called "capacitive reactance," is expressed in ohms, and abbreviated _____.

XC.

Self-induced voltage is 180° out-of-phase with the _____. When the applied voltage is at its maximum in one direction, the induced voltage is at its maximum in the opposite direction.

applied voltage.

Outside feeder tap conductors can be of unlimited length without overcurrent protection at the point they receive their supply if the conductors _____.

are suitably protected from physical damage and terminate at a single circuit breaker or a single set of fuses that limits the load to the ampacity of the conductors.

Even when power is removed from the circuit, capacitors can store large amounts of energy for a long period of time, and can discharge and arc if inadvertently shorted or grounded out.

True.

What's the maximum recommended continuous load that should be placed on 1/0 AWG aluminum conductors in a nonmetallic raceway to a panelboard located 200 ft from a 240V, single-phase power source so the NEC recommendation for voltage drop isn't exceeded?

90A.

What's the ampacity of 1/0 XHHW-2 conductors if the ambient temperature is 108°F?

148A.

What is the reactance of a 25 μF capacitor when the applied frequency is 400 Hz?

15.92 Ω.

For installations that supply only limited loads of a single branch circuit, the service disconnecting means shall have a rating not less than _____.

15A.

If a 20A branch circuit supplies multiple receptacles, the receptacles shall have an ampere rating of no less than _____.

15A.

When bonding enclosures, metal raceways, frames, and fittings, any nonconductive paint, enamel, or similar coating shall be removed at _____.

contact surfaces. threads. contact points.

Equipment and devices shall only be permitted within ducts or plenum chambers specifically fabricated to transport environmental air if necessary for their direct action upon, or sensing of, the ______.

contained air.

The waveform of the CEMF is _____ out-of-phase with the applied voltage.

180°.

Overcurrent protective devices must be designed and rated to clear fault current and must have an adequate short-circuit interrupting rating for the available fault levels. If the minimum interruption rating isn't marked on the overcurrent protective device, according to the NEC the minimum for circuit breakers is _____ and _____ for fuses.

5,000A, 10,000A.

What is the reactance of a 10 pF capacitor when the applied frequency is 30 Hz?

530.52 Ω.

Efficiency describes how much input energy is used for its intended purpose.

True.

Energy is stored in the electromagnetic field of an inductor and the electric field of a capacitor.

True.

The amount of self-induced voltage created within a winding is directly proportional to _____.

current flow. the number of wire loops (or turns). frequency at which the expanding and collapsing electromagnetic fields cut through the wires of the winding.