WorksheetsNCCER Electrical 3 Module 5
Total questions: 35
Worksheet time: 18mins
Types of fault current include overloads, short circuits, ground faults, and _____.
transient faults
symmetrical faults
asymmetric faults
arc faults
Overcurrent protection is covered in _____.
NEC Article 240
NEC Article 310
NEC Article 314
NEC Article 334
One of the first signs of worn motor bearings is MOST likely to be a(n) _____.
short circuit
ground fault
continuous overload
arc fault
Equipment intended to interrupt current at fault levels must have an interrupting rating at
nominal circuit voltage that is at least _____.
equal to the current available at the line terminals of the equipment
125% of the current available at the line terminals of the equipment
150% of the current available at the line terminals of the equipment
200% of the current available at the line terminals of the equipment
For 480V circuits, the arc current seldom exceeds _____.
20% of the available bolted fault current
40% of the available bolted fault current
60% of the available bolted fault current
80% of the available bolted fault current
A conductor with failed insulation contacts the metal edge of a grounded metal wireway.
This is known as a(n) _____.
overload
ground fault
short circuit
arc fault
The voltage rating of a fuse _____.
is always the same as the circuit voltage
can be lower than the circuit voltage but never higher
can be higher than the circuit voltage but never lower
depends upon its capability to close a circuit under an overcurrent condition
The type of fuse used to prevent nuisance tripping from temporary motor overloads and surge
currents is a(n) _____.
dual-element, time-delay fuse
Edison-base plug fuse
GE-base single-element fuse
non-time-delay fuse
UL Class R fuses have a short circuit interrupting rating of up to _____.
10,000A
50,000A
100,000A
200,000A
Which of the following is within the basic scope of Underwriters Laboratories?
Proper selection of fuses
Safety
Functional performance of fuses
Reliability of fuses
A device that is designed to withstand numerous trip and reset cycles without replacement
and can be thermal, magnetic, or solid-state is a(n) _____.
single-element relay
overload relay
fast-acting fuse
Edison-base fuse
Which of the following is TRUE with regard to circuit breakers?
Under normal conditions, the current flow bypasses the spring and latching mechanism.
Once a breaker trips, it must be replaced.
After a breaker trips, it will automatically reset itself.
Circuit breakers rarely include a thermal element.
A 500A circuit breaker has a frame size of _____.
500A
1,000A
1,200A
2,000A
What is the frame size of a 30A circuit breaker?
3A
30A
100A
1,000A
Circuit breakers are classified by _____.
manufacturer
color coding
the smallest ampere rating of its range
the largest ampere rating of its range
Which of the following is TRUE with regard to circuit breaker interrupting capacity ratings?
NEMA tests are certified by unbiased reviewers.
UL tests now include NEMA ratings.
The interrupting capacity of a circuit breaker is the same for all voltage levels.
UL tests are self-certification.
If a 120V feeder for nonmotor loads feeds a continuous load rated at 20A and a
noncontinuous load at 25A, what size overcurrent protective device should be selected?
40A
50A
60A
70A
If a continuous load on a branch circuit is measured at 12A, the overcurrent protection should
be sized at _____.
8A
10A
12A
15A
A feeder circuit with no motor load has a continuous load of 16A and a noncontinuous load
of 10A. The feeder overcurrent protective device should be sized at _____.
12A
24A
26A
30A
Which of the following is commonly referred to as motor branch circuit protection?
Component protection
Overvoltage protection
Short circuit protection
Overcurrent protection
When tripped, the circuit breaker handle moves _____.
to the On position
to the Off position
halfway between the On and Off positions
to the Reset position
The recommended method of determining short circuit currents is the _____.
momentary impedance method
peak duty method
symmetrical duty method
point-to-point method
The magnetic portion of a standard circuit breaker _____.
provides an instantaneous trip for high levels of current
protects the circuit from heat damage generated by lower level currents
prevents the device from tripping due to a short circuit
provides a trip delay for high levels of current
The thermal portion of a standard circuit breaker _____.
provides an instantaneous trip for high levels of current
protects the circuit from heat damage generated by lower level currents
prevents the device from tripping due to a short circuit
provides a trip delay for high levels of current
A single-element fuse _____.
provides an instantaneous trip for high levels of current
protects the circuit from heat damage generated by lower level currents
prevents the device from tripping due to a short circuit
provides a trip delay for high levels of current
Worn motor bearings are the most likely to result in a___.
continuous overload
short circuit
ground fault
arc fault
A high level short circuit may exceed___.
50A
500A
5,000A
50,000A
Accidental contact between an electrical conductor and a grounded enclosure is called___.
overload
short circuit
ground fault
arc fault
Most arcing faults begin as___.
ground faults
temporary overloads
sustained overloads
short circuit
A plug fuse with a hexagonal cap has a maximum amperage rating of ___.
15A
20A
25A
30A
Under normal operation and at currents near its
ampere rating, a fuse operates as a _____.
diode
resistor
conductor
heat sink
UL classifies low-voltage fuses as those operating
at _____.
24V or less
60V or less
120V or less
600V or less
A standard circuit breaker frame size is _____.
100A
300A
750A
1,500A
The interrupting capacity of a circuit breaker is
based on its rated _____.
capacitance
power factor
resistance
voltage
A feeder circuit with no motor load has a
continuous load of 10A and a noncontinuous load
of 5A. The feeder overcurrent protective device
should be sized at _____.
10A
15A
17.5A
18.75A
