Question 1

The phase voltage of a delta connection is different than the line voltage.

Accepted Answer

A) True 
 B)False

Question 2

If a load is pure resistive, the power factor has a value of unity, or 1.

Accepted Answer

A) True 
 B)False  True

Question 3

Three-phase voltages are ____ degrees apart.

Accepted Answer

A)   30
B)   90
C)   120
D)   180E) B) and C)
F) All of the above

Question 4

Figure 12-18  A delta-connected alternator is connected to a wye-connected resistive load. The alternator produces a line voltage of 240 V and the resistors have a value of 6 ohms each. Find the specified values:
-IL(Alt)  = ____ A.

Accepted Answer

A)   23.1
B)   24.2
C)   25.3
D)   26.4E) A) and C)
F) A) and D)

Question 5

Figure 12-17  A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions:
-EP(Load)  = ____ V.

Accepted Answer

A)   120
B)   240
C)   360
D)   480E) None of the above
F) C) and D)

Question 6

Figure 12-17  A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions:
-P = ____ W.

Accepted Answer

A)   53,489.29
B)   64,847.09
C)   77,232.11
D)   86,394.93E) B) and D)
F) A) and D)

Question 7

In a wye-connected system, the line voltage is higher than the phase voltage by a factor of the square root of ____.

Accepted Answer

A)   2
B)   3
C)   5
D)   7E) None of the above
F) B) and C) B

Question 8

In a wye-connected system, phase current and line current are the same.

Accepted Answer

A) True 
 B)False

Question 9

If the phase values of voltage and current are known, the apparent power can be computed using the formula VA = ____.

Accepted Answer

A)   
B)   
C)   
D)   E) All of the above
F) B) and D)

Question 10

Figure 12-17  A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions:
-IP(Load)  = ____ A.

Accepted Answer

A)   60
B)   120
C)   240
D)   480E) A) and B)
F) A) and D)

Question 11

The voltage measured across a single winding is known as the ____ voltage.

Accepted Answer

A)   wye
B)   delta
C)   phase
D)   lineE) A) and C)
F) A) and B)

Question 12

Figure 12-18  A delta-connected alternator is connected to a wye-connected resistive load. The alternator produces a line voltage of 240 V and the resistors have a value of 6 ohms each. Find the specified values:
-IL(Load)  = ____ A.

Accepted Answer

A)   23.1
B)   24.2
C)   25.3
D)   26.4E) A) and D)
F) B) and D)

Question 13

The line current of a delta connection is higher than the phase current by a factor of the square root of ____.

Accepted Answer

A)   2
B)   3
C)   5
D)   6E) B) and C)
F) All of the above

Question 14

Figure 12-17  A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions:
-IL(Alt)  = ____ A.

Accepted Answer

A)   78.22
B)   81.20
C)   103.92
D)   107.88E) B) and C)
F) None of the above C

Question 15

Figure 12-18  A delta-connected alternator is connected to a wye-connected resistive load. The alternator produces a line voltage of 240 V and the resistors have a value of 6 ohms each. Find the specified values:
-EP(Alt)  = ____ V.

Accepted Answer

A)   60
B)   120
C)   240
D)   480E) A) and B)
F) A) and C)

Question 16

Figure 12-17  A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions:
-EL(Load)  = ____ V.

Accepted Answer

A)   120
B)   240
C)   360
D)   480E) All of the above
F) A) and C)

Question 17

The phase voltage of a wye connection is less than the line voltage by a factor of the square root of 2.

Accepted Answer

A) True 
 B)False

Question 18

The horsepower rating of three-phase motors and the KVA (kilo-volt-amp)  rating of three-phase transformers is about ____% greater than for single-phase motors or transformers with a similar frame size.

Accepted Answer

A)   50
B)   100
C)   150
D)   200E) B) and D)
F) All of the above

Question 19

A single-phase alternating voltage can be produced by rotating a magnetic field through the conductors of a stationary coil.

Accepted Answer

A) True 
 B)False

Question 20

Figure 12-18  A delta-connected alternator is connected to a wye-connected resistive load. The alternator produces a line voltage of 240 V and the resistors have a value of 6 ohms each. Find the specified values:
-EP(Load)  = ____ V.

Accepted Answer

A)   133.77
B)   138.57
C)   142.47
D)   145.89E) All of the above
F) B) and C)

Exam 12: Three-Phase Circuits

The phase voltage of a delta connection is different than the line voltage.

Correct AnswerverifiedShow Answer

If a load is pure resistive, the power factor has a value of unity, or 1.

Correct AnswerverifiedTrue

Three-phase voltages are ____ degrees apart.

Correct AnswerverifiedShow Answer

Figure 12-18 A delta-connected alternator is connected to a wye-connected resistive load. The alternator produces a line voltage of 240 V and the resistors have a value of 6 ohms each. Find the specified values: -IL(Alt) = ____ A.

Correct AnswerverifiedShow Answer

Figure 12-17 A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions: -EP(Load) = ____ V.

Correct AnswerverifiedShow Answer

Figure 12-17 A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions: -P = ____ W.

Correct AnswerverifiedShow Answer

In a wye-connected system, the line voltage is higher than the phase voltage by a factor of the square root of ____.

Correct AnswerverifiedB

In a wye-connected system, phase current and line current are the same.

Correct AnswerverifiedShow Answer

If the phase values of voltage and current are known, the apparent power can be computed using the formula VA = ____.

Correct AnswerverifiedShow Answer

Figure 12-17 A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions: -IP(Load) = ____ A.

Correct AnswerverifiedShow Answer

The voltage measured across a single winding is known as the ____ voltage.

Correct AnswerverifiedShow Answer

Figure 12-18 A delta-connected alternator is connected to a wye-connected resistive load. The alternator produces a line voltage of 240 V and the resistors have a value of 6 ohms each. Find the specified values: -IL(Load) = ____ A.

Correct AnswerverifiedShow Answer

The line current of a delta connection is higher than the phase current by a factor of the square root of ____.

Correct AnswerverifiedShow Answer

Figure 12-17 A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions: -IL(Alt) = ____ A.

Correct AnswerverifiedC

Figure 12-18 A delta-connected alternator is connected to a wye-connected resistive load. The alternator produces a line voltage of 240 V and the resistors have a value of 6 ohms each. Find the specified values: -EP(Alt) = ____ V.

Correct AnswerverifiedShow Answer

Figure 12-17 A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions: -EL(Load) = ____ V.

Correct AnswerverifiedShow Answer

The phase voltage of a wye connection is less than the line voltage by a factor of the square root of 2.

Correct AnswerverifiedShow Answer

The horsepower rating of three-phase motors and the KVA (kilo-volt-amp) rating of three-phase transformers is about ____% greater than for single-phase motors or transformers with a similar frame size.

Correct AnswerverifiedShow Answer

A single-phase alternating voltage can be produced by rotating a magnetic field through the conductors of a stationary coil.

Correct AnswerverifiedShow Answer

Figure 12-18 A delta-connected alternator is connected to a wye-connected resistive load. The alternator produces a line voltage of 240 V and the resistors have a value of 6 ohms each. Find the specified values: -EP(Load) = ____ V.

Correct AnswerverifiedShow Answer

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B

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C

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