Theory Units 25-26

Question 1

A(An) _____ is an electrical connection between any two phase wires, or a phase wire and neutral wire.
Answer 1: overload
Answer 2: short circuit
Answer 3: ground fault
Answer 4: all of these

Answer 1

short circuit

Question 2

A(An) _____ occurs when an unintentional electrical connection occurs between a phase wire and metal parts of enclosures, raceways, and/or equipment.
Answer 1: overload
Answer 2: short circuit
Answer 3: ground fault
Answer 4: all of these

Answer 2

ground fault

Question 3

Fuses consist of a _____ element connected to end blades or caps, surrounded by silica sand filler material enclosed in a tube.
Answer 1: conductive
Answer 2: foam
Answer 3: light
Answer 4: nonconductive

Answer 3

conductive

Question 4

When a sustained overload occurs through the element(s) of a fuse, the heat melts _____, stopping the flow of current.
Answer 1: several elements
Answer 2: all of the elements
Answer 3: a portion of the element
Answer 4: none of these

Answer 4

portion of the element

Question 5

When a short circuit or ground fault occurs through the element of a fuse, the heat in the element rises to a point where _____ in the fuse melt to stop electrical current flow.
Answer 1: multiple conductive segments
Answer 2: a small portion of the segment
Answer 3: all of the segments
Answer 4: none of these

Answer 5

multiple conductive segments

Question 6

A _____ fuse is referred to as a nontime-delay fuse and is the least expensive type.
Answer 1: single-element
Answer 2: dual-element
Answer 3: current-limiting
Answer 4: all of these

Answer 6

single-element

Question 7

A _____ fuse is designed to clear a short circuit or ground fault in less than one-half a cycle.
Answer 1: one-time fuses
Answer 2: dual-element fuses
Answer 3: special trip fuses
Answer 4: current-limiting

Answer 7

current-limiting

Question 8

The _____ trip element of a circuit breaker operates on the time-current principle of being inversely proportional to the magnitude of the current, which means that as the overload current increases, the time it takes for the trip element to open decreases.
Answer 1: magnetic
Answer 2: electronic
Answer 3: thermal
Answer 4: none of these

Answer 8

thermal

Question 9

_____ circuit breakers permit the thermal and electromagnetic trip current and/or time settings to be adjusted to provide the user with flexibility for specific applications.
Answer 1: Inverse time
Answer 2: Adjustable trip
Answer 3: Instantaneous trip
Answer 4: all of these

Answer 9

Adjustable trip

Question 10

The time it takes for an overcurrent protective device to open is plotted on a _____ curve chart.
Answer 1: time-current characteristics
Answer 2: bar graph
Answer 3: pie chart
Answer 4: none of these

Answer 10

time-current characteristics

Question 11

As the overload current _____, the time it takes for the thermal trip element to open decreases.
Answer 1: increases
Answer 2: decreases
Answer 3: remains the same
Answer 4: none of these

Answer 11

increases

Question 12

To quickly clear a short circuit, the short-circuit _____ must rise to a level that is between ten and twenty times the rating of the circuit overcurrent protective device.
Answer 1: voltage
Answer 2: current
Answer 3: resistance
Answer 4: power

Answer 12

current

Question 13

To quickly clear a(an) _____, the ground-fault current needs to rise to a level between ten and twenty times the rating of the circuit overcurrent protective device.
Answer 1: overload
Answer 2: arcing fault
Answer 3: ground fault
Answer 4: none of these

Answer 13

ground fault

Question 14

Available short-circuit current is the _____ current in amperes that is available at a given point in the electrical system
Answer 1: phase
Answer 2: line
Answer 3: largest
Answer 4: smallest

Answer 14

largest

Question 15

The available short-circuit current is highest at the utility transformer and lowest at the _____ load because of the impedance of the circuit.
Answer 1: branch-circuit
Answer 2: feeder
Answer 3: service
Answer 4: utility transformer

Answer 15

branch-circuit

Question 16

The available short-circuit current at the _____ transformer is provided by the electric utility; no calculation is required.
Answer 1: occupancy
Answer 2: building
Answer 3: premises
Answer 4: utility

Answer 16

utility

Question 17

What is the approximate available short-circuit current on the secondary of a 50 kVA, 480V to 240V transformer having an impedance rating of 1.20 percent?
Answer 1: 10,000A
Answer 2: 12,000A
Answer 3: 14,000A
Answer 4: 17,000A

Answer 17

17,000A

Question 18

What is the approximate available short-circuit current on the secondary of a three-phase, 112.50 kVA, 480V to 208Y/120V transformer having an impedance rating of 2.40 percent?
Answer 1: 10,500A
Answer 2: 11,000A
Answer 3: 12,500A
Answer 4: 13,000A

Answer 18

13,000A

Question 19

If the protective device is not rated to _____ the available fault current at its listed voltage rating, it can explode while attempting to clear the fault.
Answer 1: interrupt
Answer 2: withstand
Answer 3: hold
Answer 4: break

Answer 19

interrupt

Question 20

Equipment must have a(an) _____ current rating that permits the protection device to clear a short circuit or ground fault without extensive damage to the equipment components.
Answer 1: overload
Answer 2: short-circuit
Answer 3: ground-fault
Answer 4: none of these

Answer 20

short-circuit

Question 21

If the equipment is not rated to _____ the available short-circuit current, it can explode while waiting for the circuit protective device to clear the fault.
Answer 1: interrupt
Answer 2: withstand
Answer 3: hold
Answer 4: break

Answer 21

break

Question 22

Selective coordination of overcurrent protective devices prevents _____ power losses to loads not part of the faulted circuit.
Answer 1: intended
Answer 2: unintended
Answer 3: excessive
Answer 4: none of these

Answer 22

unintended

Question 23

Lack of selective coordination of overcurrent protective devices can result in unintended _____ to loads not part of the faulted circuit.
Answer 1: surges
Answer 2: power losses
Answer 3: blackouts
Answer 4: shutdowns

Answer 23

power losses

Question 24

If the difference between the current leaving and returning through the current transformer of the GFCI protective device exceeds _____ (± 1 mA), the solid-state circuitry de-energizes the circuit.
Answer 1: 1 mA
Answer 2: 3 mA
Answer 3: 5 mA
Answer 4: 10 mA

Answer 24

5 mA

Question 25

A(An) _____ wire is not necessary for the proper function of a GFCI device.
Answer 1: phase
Answer 2: grounded
Answer 3: neutral
Answer 4: equipment grounding

Answer 25

equipment grounding

Question 26

GFCIs detect connections between the neutral wire and the metal parts of the electrical system (case). If a neutral connection to metal parts occurs, the GFCI protective device will _____.
Answer 1: open
Answer 2: explode
Answer 3: overload
Answer 4: none of these

Answer 26

open

Question 27

Severe electric shock or death can occur if a person touches the _____ and neutral wires at the same time, even if the circuit is GFCI protected.
Answer 1: phase
Answer 2: service
Answer 3: equipment grounding
Answer 4: none of these

Answer 27

phase

Question 28

GFCIs can only be properly tested by pressing the GFCI _____ button.
Answer 1: disconnect
Answer 2: reset
Answer 3: test
Answer 4: any of these

Answer 28

test

Question 29

A special purpose GFCI device is used in circuits where the voltage-to-ground is greater than _____.
Answer 1: 30V
Answer 2: 50V
Answer 3: 120V
Answer 4: 150Vselected

Answer 29

150V

Question 30

The current in an arcing fault is limited by the system impedance and the impedance of the arcing fault itself. Typically, at a receptacle, fault current will be above 75A, but not likely above _____.
Answer 1: 100A
Answer 2: 220A
Answer 3: 330A
Answer 4: 450A

Answer 30

450A

Question 31

A _____ arcing fault occurs when the wire within a cord is unintentionally broken, causing the current to arc across the gap in the wire.
Answer 1: series
Answer 2: parallel
Answer 3: ground
Answer 4: neutral

Answer 31

series

Question 32

_____ sources of transient voltage include the switching of utility power factor correction capacitors or lightning strikes.
Answer 1: Special
Answer 2: Interior
Answer 3: Exterior
Answer 4: any of these

Answer 32

Exterior