Residential wiring 21st 1-4 chap with
correct answers 100% 2025
1. What code sets the standard for electrical installation work in the United States? -
Correct AnswerThe NEC is the basic standard; local and state codes are to be
considered also.
What entity enforces the requirements set by the NEC? - Correct AnswerThe local
electrical inspection authority or Authority Having Jurisdiction(AHJ)
Does the NEC provide minimum or maximum standards? - Correct Answerminimum
What do the letters "UL" signify? - Correct AnswerWhen shown on an electrical product
or in a certification mark, it means the product is Listed by Underwriters Laboratories. It
also means that the product met applicable safety standards when it left the
manufacturer's plant.
What section of the NEC states that all listed or labeled equipment shall be installed or
used in accordance with any instructions included in the listing or labeling? - Correct
AnswerNEC 110.3(B)
When the word "shall" appears in an NEC reference, it means that it(must)(may) be
done. - Correct AnswerMust
What is the purpose of the NEC? What section can this statement be found in? -
Correct AnswerThe NEC states in 90.2(A) that "The purpose of this Code is the
practical safeguarding of persons and property from hazards arising from the use of
electricity."
Does compliance with the NEC always result in an electrical
installation that is adequate, safe, and efficient? Why? - Correct AnswerNo. The NEC
states in 90.2(B) that "This Code contains
provisions that are considered necessary for safety. Compliance and proper
maintenance results in an installation that is essentially free from hazard but not
necessarily efficient, convenient, or adequate for good service or future expansion of
electrical use."* Informational Note: Hazards often occur because of overloading of
wiring systems by methods or usage not in conformity with this Code.
This occurs because initial wiring did not provide for increases in the use of electricity.
An initial adequate installation and reasonable provisions for system changes will
provide for future increases in the use of electricity.
Name two nationally recognized testing laboratories. - Correct AnswerUnderwriters
Laboratories (UL) and Intertek Testing Services
(ETL listing mark). There are other testing laboratories such as
, Canadian Standards Association (CSA), Factory Mutual (FM), and others the student
might refer to that may be acceptable to the authority enforcing the Code.
a. Do Underwriters Laboratories and the other recognized testing
laboratories "approve" products?
b. What do these testing laboratories do? - Correct Answera. No. Approval is up to the
Authority Having Jurisdiction.
See NEC 90.4 and 110.2. b. They test the products for conformance to the applicable
product safety standards. When the product passes these tests, the manufacturer of the
product is then permitted to affix a "label" (often referred to as a "listing mark") that
indicates the product complied with the applicable safety standard when it left their
factory.
Does the NEC make suggestions about how to wire a house that will
be occupied by handicapped persons? - Correct AnswerInformative Annex J includes
information that is intended to assist the users of the Code in properly considering the
various
electrical design constraints of other building systems and are part of the 2010 ADA
Standards for Accessible Design. The Informative Annex is not enforceable. The basic
NEC rules still apply. Local communities, counties, states, and/or other govern-mental
bodies might have requirements. Check with your local inspection authority. Ask them if
there are any requirements or suggestions that you might need to follow.
A junction box on a piece of European equipment is marked 344 cm3.
Convert this to cubic inches. (Hint: Is there a table that lists
standard box sizes?) - Correct Answer200 0.06102 = 12.204 cubic in.
Convert 4500 watts to Btu/hour - Correct Answer4500/3.4129 = 15.358 Btu/hour
You will learn in Chapter 3 that residential lighting loads are
based on 3 volt-amperes per ft.2 (33 volt-amperes per m2). Determine
the minimum lighting load required for an area of 186 m2. Do
calculations for both feet squared and meters squared so you can see
the difference in answers. To convert meters squared to feet squared,
refer to Table 1-8. - Correct AnswerAnswer: Step 1: Convert square meters to square
feet
186 10.764 = 2002 sq. ft Step 2: 2002 3 = 6006 volts-amperes Working in metrics, the
answer is 186 33 = 6138 volt-amperes Note: This is an excellent example of what
happens when converting inch-pound units to metrics, or vice versa. You can see that
the NEC decided to "round-off" 3 volt-amperes per sq. ft to 33 volt-amperes per square
meter. The result is different answers. Not a big difference, but different nevertheless.
Converting a rounded-off inch-pound number to metrics always results in a fractional
metric value. Converting a rounded-off metric number to inch-pound units always results
in a fractional inch-pound value. There is no easy way to resolve this issue. Just follow
the values as found in the NEC. No doubt inch-pound measurements will be used in this
country for quite a while, so use the inch-pound values until more information becomes
correct answers 100% 2025
1. What code sets the standard for electrical installation work in the United States? -
Correct AnswerThe NEC is the basic standard; local and state codes are to be
considered also.
What entity enforces the requirements set by the NEC? - Correct AnswerThe local
electrical inspection authority or Authority Having Jurisdiction(AHJ)
Does the NEC provide minimum or maximum standards? - Correct Answerminimum
What do the letters "UL" signify? - Correct AnswerWhen shown on an electrical product
or in a certification mark, it means the product is Listed by Underwriters Laboratories. It
also means that the product met applicable safety standards when it left the
manufacturer's plant.
What section of the NEC states that all listed or labeled equipment shall be installed or
used in accordance with any instructions included in the listing or labeling? - Correct
AnswerNEC 110.3(B)
When the word "shall" appears in an NEC reference, it means that it(must)(may) be
done. - Correct AnswerMust
What is the purpose of the NEC? What section can this statement be found in? -
Correct AnswerThe NEC states in 90.2(A) that "The purpose of this Code is the
practical safeguarding of persons and property from hazards arising from the use of
electricity."
Does compliance with the NEC always result in an electrical
installation that is adequate, safe, and efficient? Why? - Correct AnswerNo. The NEC
states in 90.2(B) that "This Code contains
provisions that are considered necessary for safety. Compliance and proper
maintenance results in an installation that is essentially free from hazard but not
necessarily efficient, convenient, or adequate for good service or future expansion of
electrical use."* Informational Note: Hazards often occur because of overloading of
wiring systems by methods or usage not in conformity with this Code.
This occurs because initial wiring did not provide for increases in the use of electricity.
An initial adequate installation and reasonable provisions for system changes will
provide for future increases in the use of electricity.
Name two nationally recognized testing laboratories. - Correct AnswerUnderwriters
Laboratories (UL) and Intertek Testing Services
(ETL listing mark). There are other testing laboratories such as
, Canadian Standards Association (CSA), Factory Mutual (FM), and others the student
might refer to that may be acceptable to the authority enforcing the Code.
a. Do Underwriters Laboratories and the other recognized testing
laboratories "approve" products?
b. What do these testing laboratories do? - Correct Answera. No. Approval is up to the
Authority Having Jurisdiction.
See NEC 90.4 and 110.2. b. They test the products for conformance to the applicable
product safety standards. When the product passes these tests, the manufacturer of the
product is then permitted to affix a "label" (often referred to as a "listing mark") that
indicates the product complied with the applicable safety standard when it left their
factory.
Does the NEC make suggestions about how to wire a house that will
be occupied by handicapped persons? - Correct AnswerInformative Annex J includes
information that is intended to assist the users of the Code in properly considering the
various
electrical design constraints of other building systems and are part of the 2010 ADA
Standards for Accessible Design. The Informative Annex is not enforceable. The basic
NEC rules still apply. Local communities, counties, states, and/or other govern-mental
bodies might have requirements. Check with your local inspection authority. Ask them if
there are any requirements or suggestions that you might need to follow.
A junction box on a piece of European equipment is marked 344 cm3.
Convert this to cubic inches. (Hint: Is there a table that lists
standard box sizes?) - Correct Answer200 0.06102 = 12.204 cubic in.
Convert 4500 watts to Btu/hour - Correct Answer4500/3.4129 = 15.358 Btu/hour
You will learn in Chapter 3 that residential lighting loads are
based on 3 volt-amperes per ft.2 (33 volt-amperes per m2). Determine
the minimum lighting load required for an area of 186 m2. Do
calculations for both feet squared and meters squared so you can see
the difference in answers. To convert meters squared to feet squared,
refer to Table 1-8. - Correct AnswerAnswer: Step 1: Convert square meters to square
feet
186 10.764 = 2002 sq. ft Step 2: 2002 3 = 6006 volts-amperes Working in metrics, the
answer is 186 33 = 6138 volt-amperes Note: This is an excellent example of what
happens when converting inch-pound units to metrics, or vice versa. You can see that
the NEC decided to "round-off" 3 volt-amperes per sq. ft to 33 volt-amperes per square
meter. The result is different answers. Not a big difference, but different nevertheless.
Converting a rounded-off inch-pound number to metrics always results in a fractional
metric value. Converting a rounded-off metric number to inch-pound units always results
in a fractional inch-pound value. There is no easy way to resolve this issue. Just follow
the values as found in the NEC. No doubt inch-pound measurements will be used in this
country for quite a while, so use the inch-pound values until more information becomes
