C 10 Electrical Exam Part VI Questions With Complete
Solutions
A 20-ampere ac snap switch may disconnect a 2-horsepower
motor with a maximum full-load current of _____.
A-16 amperes
B-10 amperes
C-20 amperes
D-18 amperes Correct Answers The Correct Answer Is A
A snap switch used to disconnect a motor must be derated 80
percent. Therefore, 20 amperes x .80 = 16 amperes. NEC
430.109(C)(2).
A 240-volt single-phase motor is a single motor unit if its rating
is not more than _____.
A-20 amperes
B-30 amperes
C-40 amperes
D-50 amperes Correct Answers The Correct Answer Is C
NEC Section 440.62(A)(2) specifies that an air conditioner shall
be considered a single motor unit if its rating is not more than 40
amperes and 250 volts, single phase.
A branch circuit is supplying a single hermetic refrigerant
motor-compressor for an air conditioning unit in a single-family
dwelling. The hermetic refrigerant motor-compressor rated-load
current is 18 amperes. If a 30-ampere fuse will not carry the
motor compressor s starting current, the maximum rating of the
branch-circuit overcurrent protective device may be increased to
_____.
A-35 amperes
,B-40 amperes
C-45 amperes
D-50 amperes Correct Answers The Correct Answer Is B
The protective device can be increased also, but shall not exceed
225 percent of the motor rated-load current or branch-circuit
selection current, whichever is greater. NEC 440.22(A).
A branch circuit supplying fluorescent lamps in a sign must not
be rated more than _____.
A-20 amperes
B-15 amperes
C-30 amperes
D-40 amperes Correct Answers The Correct Answer Is A
Circuits supplying incandescent, fluorescent, and high-intensity-
discharge lamp forms must be rated not more than 20 amperes.
NEC Section 600.5(B)(1).
A disconnecting means for a 2300-volt motor must be capable of
being locked in the _____.
A-closed position
B-open and closed position
C-open position
D-ON position Correct Answers The Correct Answer Is C
All motors must be connected to a disconnecting means.
However, motors over 600 volts must also be provided with
means of locking the disconnect open so that it cannot be
inadvertently closed when someone is working on the motor.
NEC 430.127.
,A dust-ignition-proof enclosure supplied by a horizontal
raceway does not require a raceway seal if the conduit length is
at least _____.
A-10 feet
B-5 feet
C-8 feet
D-12 feet Correct Answers The Correct Answer Is A
Where a raceway provides communication between an enclosure
that is required to be dust-ignition-proof and one that is not,
suitable means shall be provided to prevent the entrance of dust
into the dust-ignition-proof enclosure through the raceway. One
of the following means shall be permitted: (1) a permanent and
effective seal; (2) a horizontal raceway not less than 10 feet
long; or (3) a vertical raceway not less than 5 feet long and
extending downward from the dust-ignition-proof enclosure.
NEC Section 502.5.
A hazardous location in which breakdown or faulty operation of
equipment or processes might release ignitable concentrations of
flammable gases or vapors, and might also cause simultaneous
failure of electric equipment is classified as a _____.
A-Class I, Division 1 location
B-Class I, Division 2 location
C-Class II, Division 1 location
D-Class II, Division 2 location Correct Answers The Correct
Answer Is A
NEC Section 500.5(B)(1) also specifies the conditions in this
question as Class I, Division 1.
, A hazardous location in which ignitable concentrations of
flammable gasses or vapors can exist under normal operating
conditions is classified as a _____.
A-Class I, Division 1 location
B-Class I, Division 2 location
C-Class II, Division 1 location
D-Class II, Division 2 location Correct Answers The Correct
Answer Is A
NEC Section 500.5(B)(1) specifies the above condition to be
Class I, Division 1.
A hazardous location in which ignitable concentrations of gases
or vapors may exist frequently because of repair or maintenance
operations or because of leakage is classified as _____.
A-Class I, Division 1 location
B-Class I, Division 2 location
C-Class II, Division 1 location
D-Class II, Division 2 location Correct Answers The Correct
Answer Is A
NEC Section 500.5(B)(1) also specifies the conditions in this
question as Class I, Division 1.
A location in which flammable gasses or vapors are or may be
present in the air in quantities sufficient to produce explosive or
ignitable mixtures is classified as a _____.
A-Class IV location
B-Class III location
C-Class II location
D-Class I location Correct Answers The Correct Answer Is D
NEC Section 500.5(B)(1) specifies the above condition to be
Class I location.
Solutions
A 20-ampere ac snap switch may disconnect a 2-horsepower
motor with a maximum full-load current of _____.
A-16 amperes
B-10 amperes
C-20 amperes
D-18 amperes Correct Answers The Correct Answer Is A
A snap switch used to disconnect a motor must be derated 80
percent. Therefore, 20 amperes x .80 = 16 amperes. NEC
430.109(C)(2).
A 240-volt single-phase motor is a single motor unit if its rating
is not more than _____.
A-20 amperes
B-30 amperes
C-40 amperes
D-50 amperes Correct Answers The Correct Answer Is C
NEC Section 440.62(A)(2) specifies that an air conditioner shall
be considered a single motor unit if its rating is not more than 40
amperes and 250 volts, single phase.
A branch circuit is supplying a single hermetic refrigerant
motor-compressor for an air conditioning unit in a single-family
dwelling. The hermetic refrigerant motor-compressor rated-load
current is 18 amperes. If a 30-ampere fuse will not carry the
motor compressor s starting current, the maximum rating of the
branch-circuit overcurrent protective device may be increased to
_____.
A-35 amperes
,B-40 amperes
C-45 amperes
D-50 amperes Correct Answers The Correct Answer Is B
The protective device can be increased also, but shall not exceed
225 percent of the motor rated-load current or branch-circuit
selection current, whichever is greater. NEC 440.22(A).
A branch circuit supplying fluorescent lamps in a sign must not
be rated more than _____.
A-20 amperes
B-15 amperes
C-30 amperes
D-40 amperes Correct Answers The Correct Answer Is A
Circuits supplying incandescent, fluorescent, and high-intensity-
discharge lamp forms must be rated not more than 20 amperes.
NEC Section 600.5(B)(1).
A disconnecting means for a 2300-volt motor must be capable of
being locked in the _____.
A-closed position
B-open and closed position
C-open position
D-ON position Correct Answers The Correct Answer Is C
All motors must be connected to a disconnecting means.
However, motors over 600 volts must also be provided with
means of locking the disconnect open so that it cannot be
inadvertently closed when someone is working on the motor.
NEC 430.127.
,A dust-ignition-proof enclosure supplied by a horizontal
raceway does not require a raceway seal if the conduit length is
at least _____.
A-10 feet
B-5 feet
C-8 feet
D-12 feet Correct Answers The Correct Answer Is A
Where a raceway provides communication between an enclosure
that is required to be dust-ignition-proof and one that is not,
suitable means shall be provided to prevent the entrance of dust
into the dust-ignition-proof enclosure through the raceway. One
of the following means shall be permitted: (1) a permanent and
effective seal; (2) a horizontal raceway not less than 10 feet
long; or (3) a vertical raceway not less than 5 feet long and
extending downward from the dust-ignition-proof enclosure.
NEC Section 502.5.
A hazardous location in which breakdown or faulty operation of
equipment or processes might release ignitable concentrations of
flammable gases or vapors, and might also cause simultaneous
failure of electric equipment is classified as a _____.
A-Class I, Division 1 location
B-Class I, Division 2 location
C-Class II, Division 1 location
D-Class II, Division 2 location Correct Answers The Correct
Answer Is A
NEC Section 500.5(B)(1) also specifies the conditions in this
question as Class I, Division 1.
, A hazardous location in which ignitable concentrations of
flammable gasses or vapors can exist under normal operating
conditions is classified as a _____.
A-Class I, Division 1 location
B-Class I, Division 2 location
C-Class II, Division 1 location
D-Class II, Division 2 location Correct Answers The Correct
Answer Is A
NEC Section 500.5(B)(1) specifies the above condition to be
Class I, Division 1.
A hazardous location in which ignitable concentrations of gases
or vapors may exist frequently because of repair or maintenance
operations or because of leakage is classified as _____.
A-Class I, Division 1 location
B-Class I, Division 2 location
C-Class II, Division 1 location
D-Class II, Division 2 location Correct Answers The Correct
Answer Is A
NEC Section 500.5(B)(1) also specifies the conditions in this
question as Class I, Division 1.
A location in which flammable gasses or vapors are or may be
present in the air in quantities sufficient to produce explosive or
ignitable mixtures is classified as a _____.
A-Class IV location
B-Class III location
C-Class II location
D-Class I location Correct Answers The Correct Answer Is D
NEC Section 500.5(B)(1) specifies the above condition to be
Class I location.
