Question 1

Some fuses are designed to delay for a period of time before they open. These fuses are often referred to as time-delay fuses or ____ fuses.

Accepted Answer

Time-delay fuses are commonly known as slow-blow fuses. They have a built-in delay before they open to allow for temporary surges in current, while still providing protection against sustained overloads. This is especially useful in circuits with high inrush currents or motor starting currents. The other options, breaker, measured-response, and quick-start, do not accurately describe the function of time-delay fuses.

Question 2

The type of three-phase service is determined by the type of secondary transformer connection supplied by the power company.

Accepted Answer

The type of three-phase service (e.g., delta or wye) is determined by how the secondary side of the transformer is connected, which is controlled by the power company based on the specific service requirements and standards.

Question 3

The wire size is determined by the ____ rating of the circuit.

Accepted Answer

The wire size is determined by the ampere rating of the circuit. The higher the amperage, the larger the wire size required to handle the current safely without overheating. Voltage, reactance, and turns ratio do not directly determine wire size.

Question 4

When aluminum is used for the bus material, an antioxidant compound should be used to prevent ____.

Accepted Answer

Aluminum is susceptible to corrosion and can form a layer of oxide on its surface, which can weaken the material and cause structural problems. Therefore, an antioxidant compound should be used to prevent corrosion when aluminum is used for the bus material.

Question 5

Standard size circuit breakers are approximately ____ inch(es) in width.

Accepted Answer

Standard size circuit breakers are approximately 1 inch in width. This is a common size for residential and many commercial breakers, allowing for compact yet accessible electrical panel layouts.

Question 6

The fall-of-potential test requires the use of a ground resistance meter.

Accepted Answer

The fall-of-potential test is a method for measuring the resistance of an earthing system, which requires the use of a ground resistance meter.

Question 7

There are three main tests used to measure ground resistance. One of these is the ____.

Accepted Answer

The answer of There are three main tests used to...

Question 8

When making a 240-V single-phase connection with neutral, the ____ conductors are connected to the poles of the circuit breaker.

Accepted Answer

In a 240-V single-phase connection with neutral, the black and red conductors are typically used as the hot wires connected to the poles of the circuit breaker, while the white wire serves as the neutral and the bare or green wire as the ground.

Question 9

Many circuit breaker panels are designed to employ half-size circuit breakers.

Accepted Answer

This is true. Half-size circuit breakers allow for more circuits to be installed in the panel, as they take up less space than full-size circuit breakers.

Question 10

Table 14-2 
-Assume a branch circuit rated at 90 A is to be installed using copper wire with type THW insulation. Use the accompanying table to determine what size conductor should be used for this installation.

Accepted Answer

#2 AWG copper conductor is suitable for 90 A circuits with THW insulation according to the National Electrical Code (NEC) ampacity tables.

Question 11

Fuses are connected in series with the load.

Accepted Answer

Fuses are typically connected in series with the load to protect it from excessive current. When the current in the circuit exceeds the fuse's rated capacity, the fuse will blow and break the circuit, preventing any further damage to the load or the wiring.

Question 12

The three-phase three-wire system is made by connecting the ____ windings of a three-phase transformer bank in ____ and connecting the three lines to a three-phase panel.

Accepted Answer

The three-phase three-wire system can be created by connecting either the primary or secondary windings of a three-phase transformer bank in either wye (Y) or delta (Δ) configuration. This flexibility allows for various types of connections to match the specific requirements of the electrical distribution system.

Question 13

Table 14-2 
-A branch circuit rated at 150 A is to be installed using aluminum wire with type THHW insulation. Use the accompanying table to determine what size conductor should be used for this installation.

Accepted Answer

The answer of Table 14-2 
-A branch circuit rated at...

Question 14

Proper grounding helps protect against ____ currents, electrical noise, and lightning strikes.

Accepted Answer

Proper grounding helps protect against transient currents, which can cause damage to electronic equipment, as well as electrical noise, which can interfere with signal transmissions. It can also protect against lightning strikes by providing a low-resistance path for the current to flow into the ground, rather than passing through buildings and other equipment. Continuous currents, transformed currents, and closed loop currents are not typically the primary concerns addressed by proper grounding.

Question 15

____-pole circuit breakers are used to connect three-phase circuits.

Accepted Answer

Three-pole circuit breakers are used to connect three-phase circuits.

Question 16

The clamp-on ground resistance test has several advantages over the three-point fall-of-potential test.

Accepted Answer

The clamp-on ground resistance test is faster, easier to set up, and can be performed on energized systems, while the three-point fall-of-potential test requires a larger setup time and cannot be used on energized systems. It also provides more accurate readings in areas with low soil resistance.

Question 17

In theory, the system ground is considered to have a resistance of ____.

Accepted Answer

In theory, the system ground is considered to have zero resistance because it is an ideal connection point between the electrical system and the earth. However, in practice, there may be some resistance due to soil conditions, moisture level, and other factors.

Question 18

Circuit breakers that operate by heat are known as ____ circuit breakers.

Accepted Answer

Circuit breakers that operate by heat are known as thermal circuit breakers. They use a bimetallic strip that heats up and bends to trip the breaker when the current exceeds the rated limit. Fuses (Option A) are also used for overcurrent protection, but they operate by melting a thin wire and breaking the circuit. Magnetic (Option B) and electrical (Option C) circuit breakers operate on different principles and do not rely on heat.

Question 19

The three-phase four-wire high-leg connection is made by connecting the secondary windings of a three-phase transformer bank in delta or open delta and center tapping one of the transformer secondaries to provide a(n) ____ conductor.

Accepted Answer

The high-leg connection requires a neutral conductor that is center tapped. This neutral conductor is used for grounding and provides a reference point for single-phase loads. The high-leg connection is sometimes called a "wild leg" or "stinger" connection because the voltage on the high-leg (or stinger) is higher than the voltage on the other two legs.

Question 20

In a single-phase service, ____ V is available from the center tap to either end of the secondary winding.

Accepted Answer

In a single-phase service, 120 volts is available from the center tap to either end of the secondary winding. This is because the voltage across each half of the secondary winding is 120 volts in relation to the center tap, so the total voltage from one end to the other is 240 volts.

Quiz 15: Electrical Services