Part 1
If the protection device is not rated to interrupt the current at the available fault at its listed voltage rating, it can explode while attempting to clear the fault.
true
Metal parts of premises wiring must be bonded to a low-impedance path designed so that the circuit protection device will quickly open and clear a ground fault.
true
Unsafe arcing faults can occur in one of two ways, as series arcing faults or as parallel arcing faults. The most dangerous is the parallel arcing fault
true
When power supplies are connected in parallel, the voltage remains the same, but the current or amp-hour capacity will be increased.
true
Factors that affect the available short-circuit current include transformer ______
voltage, kVA rating, and impedance
When a motor starts, the current drawn is approximately ____ times the motor FLA; this is known as "motor locked-rotor amperes" (LRA).
6
How many 20A, 120V circuits are required for forty-two, 300W luminaires (noncontinuous load) that have a power factor of 85 percent?
7 circuits
Lightning protection is intended to protect the building itself, as well as the electrical equipment on or inside the structure
False
Nonmetallic metals are ferrous, meaning they do not contain any iron, and cannot e magnetized.
False
If the rotating part of the motor winding is jammed so that it cannot rotate, no CEMF will be produced in the motor winding. Result-the motor operates at _____ and the windings will be destroyed by excessive heat.
LRC
The PIE formula circle demonstrates the relationship between power, current, voltage, and is expressed in the formula
P = I x E transposed to I = P/E or E = P/I
the power of each resistor is determined by what formula
P = I^2 x R I^2 = Current of circuit squared R= Resistance of the resistor
When current flows through a resistor, power is consumed. The power consumed by each branch of the parallel circuit is determined by the formulas:
P = I^2 x R P = E x I P= E^2/R
_____ motors are fractional horsepower motors that operate equally well on ac and dc and are used for vacuum cleaners, electric drills, mixers, and light household appliances
Universal
The opposition offered to the flow of ac current by a capacitor is called "capacitive reactance" which is expressed in ohms and abbreviated ________
Xc
Self-induced voltage opposes the change in current flowing in the conductor. This is called "inductive reactance" and it is abbreviated ______
Xl
The abbreviation for impedance is
Z
A GFCI-protection device contains an internal monitor that repents the device from being turned on if there is a neutral-to-case connection downstream of the device, but this only occurs if there is a load on the circuit
false
A holding relay is primarily used for worker convenience.
false
Because of the dangers associated with an open neutral conductor, the continuity of the _____ conductor cannot be dependent upon the receptacle.
grounded
The total opposition to current flow in ac circuits is called "____" and measured in ohms.
impedance
A clamp-on ac ammeter has a coil that is clamped around the conductor and detects the rising and falling _____ field being produced due to the ac flow through the conductor.
magnetic
In a direct-current circuit, the only opposition to current flow is the physical resistance of the material through which the current flows.
resistance and is measured in ohms.
The _____ of a generator is forced to rotate while it is being subjected to the magnetic field if the stator.
rotor
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
series circuit
The magnetic time-delay circuit breaker operate on the solenoid principle where a movable core, held with a spring, is moved by the magnetic field of a(n) _______
short circuit or ground flat
Equipment must have a(n) ______ current rating that permits the protection device to clear a short circuit or ground fault without excessive damage to the components of the circuit
short-circuit
The expanding and collapsing magnetic field within the conductor induces a voltage in the conductors (CEMF) that repels the flowing electrons toward the surface of the conductor. This is called "____."
skin effect
In a(n) ______ motor, the rotor is locked in step with the rotating stator field and is dragged long at the speed of the rotating magnetic field.
synchronous
Alternating-current: three factors that oppose current flow
the resistance material; the inductive reactance of the circuit; and the capacitive reactance of the circuit
Kirchoff's Current Law state, "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.
thermo
The effective value is equal to the peak value _____
times 0.707
According to the Electron Current Flow Theory, electrons flow away from the negative terminal of the source, through the circuit and load, toward the positive terminal of the source.
true
An AFCI-protection device provides protection from am arcing fault by recognizing the characteristics unique to an arcing fault and by functioning to de-energize the circuit when an arc fault is detected
true
Available short-circuit current is the current in amperes available at a given point in the electrical system
true
Circuit breakers and fuses are intended to interrupt the circuit, and they must have an ampere interrupting rating (AIR) sufficient for the available short circuit current.
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
Even when power is removed from the circuit, capacitors can store large amounts of energy for a long period of time. They can discharge and arc if inadvertently shorted or grounded out.
true
An electrical arc blast can approach _____, which vaporizes metal parts and produces an explosive and deadly pressure wave.
30,000*f
What is the conductor power loss in watts for a 120V circuit that has a 3 percent voltage drop and carries a current flow of 12A?
43W
Arcing is defined as luminous discharge of electricity across an insulating medium. Electric arcs operate at temperatures between ______ and expel small particles of very hot molten material.
5,000 and 15,000^F
What is the nameplate FLA for 20 hp, 208V, three-phase motor with 90 percent power factor and 80 percent efficiency?
58A
What is the voltage drop of two 12 AWG conductors (0.40 ohms) supplying a 16A load, located 100ft from the power supply? Formula: E 1 x R
6.40V
Describes a method of connecting electrical components so there are two or more paths through which current may flow
Parallel
The electric motor works on the principle of the attracting and repelling forces of ____ fields.
magnetic
Factors that affect the available short-circuit current include circuit conductor______
material, size, and length
A nonsinusoidal waveform is created when _____ loads distort the voltage and current sine wave.
nonlinear
If the ungrounded conductors of a multiwire circuit are not terminated to different phases, this can cause the neutral current to be in excess of the neutral conductor rating.
true
In an ac induction motor, the stator produces a rotating magnetic field that induces current in the rotor windings. The rotor current generates a magnetic field in opposition to the magnetic field of the stator, thereby causing the rotor to turn
true
Parallel circuits are used for most building wiring
true
Severe electric chock or death can occur if a person touches the ungrounded and the neutral conductors at the same time, even if the circuit is GFCI-protected
true
The current flowing on the neutral conductor of a multiwire circuit is called "unbalanced current."
true
Typically, when a GFCI-circuit device fails, the switching contacts remain closed and the device will continue to provide power without GFCI protection
true
When describing the relationship between voltage and current, the reference waveform is always ____
voltage
Magnetic lines of force can cross each other and they are called flux lines.
False
The best conductors, in order of their conductivity, are gold, silver, copper, and aluminum.
False
The motor FLA rating is used when sizing motor conductor size or circuit protection.
False
The termination of the lighting stroke is unlikely to ignite combustible materials.
False
To prevent fires and electric shock, the NEC specifies that neutral current flow on metal parts of the electrical system.
False
Ohm's Law expresses the relationship between a direct-current circuit's current intensity (I), electromotive force (e), and its resistance (r).
Formula: I = E/R
Increasing one factor results in a decrease in another factor by the same magnitude, or a decrease in one factor will result in an increase of the same magnitude in another factor.
Inverse proportion
The total current provided by the source to a parallel circuit is equal to the sum of the currents of all of the branches
Kirchoff's Current Law I = E/R E = voltage of each branch R = Resistance of each branch (appliance)
In a series, the sum of the voltage across all of the resistors ( or "voltage drops") in a series circuit is equal to the applied voltage
Kirchoff's Voltage Law
Kirchoff's Voltage Law states, 'in a series circuit, the sum of the voltage drops across all of the resistors will equal the applied voltage."
True
Lighting frequently terminates to a point of elevation and strikes nonmetallic as well as metallic objects with the same frequency.
True
People become injured and death occurs when voltage pushes electrons though the human body causing the heart to go into ventricular fibrillation.
True
Providing a path to the earth often helps reduce electrostatic charge.
True
The major advantage of ac over dc is the ease of voltage regulation by use of a transformer.
True
The opposition to current flow results in voltage drop.
True
The severity of an electric shock is dependent on the current flowing through the body, which is impacted by circuit voltage and contact resistance.
True
The formulas in the power wheel apply to ________
dc and ac with unity power factor
For ac circuits, the ac _____ of a conductor must be taken into consideration.
eddy currents skin effect resistance
The total resistance of a parallel circuit can be calculated by the ____ method.
equal resistance, product-over-sum, reciprocal
What does it cost per year (at 8 cents per kWh) for the power loss of a 12 AWG circuit conductor (100ft long) that has a total resistance of 0.40 ohm and current flow of 16A?
$70
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 will be ______ percent of the ungrounded conductor current.
0
What is the resistance of the circuit conductors when the conductor voltage drop is 7.20V and the current flow is 50A?
0.14ohms
The total circuit resistance of two 12 AWG conductors (each 100ft long) is 0.40 ohms. If the current of the circuit is 16A, what is the power loss of the conductors in watts?
100W
If the output is 1,600W and the equipment is 68 percent efficient, what are the input amperes at 120V?
15A
What is the power loss in watts of a conductor that carries 24A and has a voltage drop of 7.20V?
175W
What is the power consumed by a 10 kW heat strip rated 230V connected to an 116V circuit?
2.50kW
What size transformer is required for a 100A, 240, single-phase noncontinuous load that has a power factor of 85 percent?
25 kVA
What is the approximate power consumed by a 10 kW heat strip rated 230V, when connected to a 208V circuit?
8.20kW
The induced voltage in a conductor carrying alternating current opposes the change in current flowing through the conductor. The induced voltage that opposes the current flow is called "______."
CEMF counter-electromotive force back-EMF
Changing one factor in a direct change to another factor in the same direction and by the same magnitude.
Direct proportion
Ohm's Law circle Formula circle ( the relationship between current, voltage, and resistance
E = I x R I = E/R R=E/I
AC inductive or capacitive reactive loads cause he voltage and current to be in-phase with each other.
False
In a dc circuit, the only opposition to current flow if the physical resistance of material. This opposition is called 'reactance' and is measure in ohms.
False
Inverse time breakers operate on the principle that as the current decreases, the time it takes for the device to open decrease.
False
Ohmmeters measure the ____ or opposition to current flow of a circuit or component.
Resistance
Accordin to Kirchoff's Current Law, the total current provided by the source to a parellel circuit will equal the sum of the currents of all of the branches
True
According to the Conventional Current Flow Theory, electrons travel from positive to negative.
True
If a conductor carrying current is next to another conductor carrying current in the opposite direction, the electromagnetic field attempts to push the conductors apart.
True
It is not the force of the magnetic field through a conductor that produces electricity; it is the relative motion of the field to the electrons within the conductor that produces the movement of electrons.
True
The purpose of overcurrent protection is to protect the 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, short circuit, or ground flat
To protect against electric shock or to prevent a fire, a dangerous _____ must quickly be removed by opening thee circuit's overcurrent protection device.
overload, short circuit, or ground flat
Improper wiring or mishandling of mutilwire branch circuits can cause ____ connected to the circuit.
overloading of the neutral conductors and destruction of equipment because of overvoltage
Dual-voltage ac motors are made with two field windings. The field windings are connected in _____ for low-voltage operation and in ____ for high-voltage operation
parallel, series
Because of the earth's high resistance to current flow, it cannot be used for the purpose of cleaning a line-to-case ground fault for _____ wiring.
premises
The megger is used to measure very high- _____ values, such as those found in cable insulation, or motor and transformer windings.
resistance
