Chapter 13 Review Questions & Workbook
A GFCI opens when as little as _____ amperes leaks out of a circuit and into the grounding circuit.
0.006 (6 milliamperes)
To calculate an alternating current's root means square voltage, multiply the maximum voltage value by _____.
0.707 example... V(rms) = V(max) x 0.707
The actual power used by a circuit is the _____ power of the circuit.
True
True or false? A class 2 circuit is defined as the portion of a wiring system between the power source and the connected equipment, assuming the power source has an output no greater than 30V and 1000VA.
True
True or false? A class 2 circuit is defines as a circuit supplied by a power source that has an output no greater than 30V and 1000VA.
True
True or false? In an electrical circuit, inductive components can cause voltage and current to be out of phase.
True
True or false? The effective voltage of an ac power source is calculated the same as rms voltage.
True
True or false? Three phase power has separate voltage signals that are delayed so they peak at different times.
True
True or false? Unintentional electrical resistance may result from improperly sized conductors.
True
The hot wires connected to the phase lines of a transformer.
Ungrounded conductors
An ____ is a condition in which a circuit's voltage is reduced without intent or outside of the normal design.
Unintentional Voltage drop
The effective voltage of an alternating current is calculated using the formula _____.
V(max) x 0.707
What is the formula for calculating a conductor's voltage drop?
VD = 2 x L x R x I ÷ 1000
Which electrical problem involves a circuit's applied voltage being reduced along a conductor to a level that is too low for safe use on the electrical load?
Voltage drop
Capacitive reactance affects the true power of a circuit because it causes ____.
Voltage to lag behind current
True or false? A megawatt is equal to one thousand watts.
False
True or false? Capacitive reactance does not produce resistance to the flow of alternating current.
False
True or false? Class 2 circuits do not include remote-control circuits with a relay, thermostat or any other device that controls any other circuit.
False
True or false? If an electrical circuit is purely resistive, it's apparent power cannot equal its true power.
False
True or false? Resistance causes a phase shift in which current lags behind voltage.
False
True or false? There is no difference between a 4 AWG wire and a 4/0 AWG wire.
False
True or false? Voltage and current are out of phase when they both reach their positive and negative peaks at the same time.
False
A form of circuit protection that contains a metal conductor that melts to open a circuit when current is too high is a _____.
Fuse
An overcurrent protection device that is designed to heat up and melt to stop high current is a _____.
Fuse
The ground wire in an HVACR electrical circuit is always _____.
Green
The soil to which an electrical system connect.
Ground
A _____ is a condition in which a current-carrying conductor touches a grounded object.
Ground fault
Which electrical problem creates a dangerous electrical shock situation that involves a device or ungrounded metal becoming electrically hot or live.
Ground fault
A form of circuit protection that opens the circuit if it detects an imbalance between the ungrounded and grounded wires of a circuit is a _____.
Ground fault circuit interrupter (GFCI)
An overcurrent protection device that detects current imbalances between ungrounded and grounded conductors is a _____.
Ground fault circuit interrupter (GFCI)
The neutral wires connected to a transformer.
Grounded conductors
The connection of an electrical system to the earth or the equipment that connects the system to the earth.
Grounding
An ungrounded conductor is also sometimes called a _____.
Hot wire
If the maximum current of an ac power source peaks at 6A, what is the effective current?
I(rms) = I(max) x 0.707 I(rms) = 6A x 0.707 = 4.242A
When voltage and current reach their positive and negative peaks at the same time in a alternating current cycle, they are said to be _____.
In phase
The numbers for aught sizes _____ as the wire size increases.
Increase
The numbers for aught size wires increase as the wire size _____.
Increases
An electrical property that opposes a change in current.
Inductance
The electrical property that opposes a change in current is called _____.
Inductance
In an electrical circuit, current may be caused to lag behind voltage due to _____.
Inductive reactance
If the true power and apparent power are not equal, the power factor of a circuit is _____.
Less than 100%
Local electrical codes often use standards set by the _____.
NEC (National Electrical Code)
Inductive reactance is measured in _____.
Ohms
An _____ occurs when a break in the electrical path stops a circuit's current.
Open circuit
Which electrical problem is a break in a current's path resulting from a bad electrical connection, broken wire, open fuse or circuit breaker, or a burned out component?
Open circuit
An _____ is a condition in which too much current flows through a circuit.
Overload
Which electrical problem involves overcurrent due to an incorrect power supply, equipment failure, too many loads connected, or electromechanical operating under strain?
Overload
What is the power used by an electric motor that draws a current of 15A from a 240V power source?
P = I x E P = 15A x 240V P = 3600W
When current flows through an electrical component due to a potential difference, electrical _____ is produced.
Power
The ratio of true power to apparent power is the _____ of a circuit.
Power factor
The difference between power output and power input is _____.
Power loss
_____ values are used to equate the heat produced by alternating current to direct current values that would produce the same amount of heat.
Root mean square
A _____ occurs when current is routed around an electrical load instead of through it.
Short circuit
Which electrical problem involves extremely high current going around an electrical load?
Short circuit
Which electrical problem is most likely to blow a fuse or trip a circuit breaker immediately as it occurs.
Short circuit
As little as _____ milliamperes leaking out of a circuit will cause a GFCI to open.
6
Electrical wire size is specified by the _____.
American Wire Gage (AWG)
Calculated value that does not take into account the effects of inductive reactance or capacitive reactance.
Apparent power
Which of the following values is always calculated in volt-amperes?
Apparent power
A form of circuit protection that only regulates current flow by changing its resistance based on heat is a _____.
Thermistor
An overcurrent protection device that regulates current by changing its resistance based on heat is a _____.
Thermistor
The most widely used polyphase power arrangement used in HVACR is _____ power.
Three-phase
In a three-phase voltage cycle, three separate voltage signals are delayed so they peak at different _____.
Times
A circuit's power factor shows the relationship between a circuit's _____ power and apparent power.
True
As a conductors wire diameter increases, its AWG number _____.
Decreases
How many watts does an electrical load use if a current of 1A flows through it when the load is connected to a 1V power source?
1W
The power source that supplies power to a Class 2 circuit cannot have an output greater than _____.
30V and 1000VA
As wire diameter size increases, its electrical resistance _____.
Decreases
Electricity distributed in North America has a frequency of _____ Hz.
60
Since resistance limits the flow of current, it causes _____.
A voltage drop
Joining all the metallic components of an electrical system, even those that do not normally carry current, is defined as _____.
Bonding
The creation of a continuous electrical connection of all metal parts in an electrical system.
Bonding
An electrical property that opposes a change in voltage?
Capacitance
In an electrical circuit, voltage voltage may be caused to lag behind current due to _____.
Capacitive reactance
A form of circuit protection that employs a solenoid to open the circuit if current exceeds predetermined level is a _____.
Circuit breaker
An overcurrent protection device that uses a solenoid to open the circuit when current rises to a preset limit is a _____.
Circuit breaker
Inductive reactance affects the true power of a circuit because it causes _____.
Current to lag behind voltage
