A three-phase -connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I θa = 12 30° A, what are the polar expressions for the other phase currents?

I θb = 12120° A, I θc = 1230° A

I θb = 12 150° A, I θc = 12–90° A

I θb = 12120° A, I θc = 1230° A

I θb = 1230° A, I θc = 12120° A

I θb = 1290° A, I θc = 1290° A

Compare the total copper cross sections in terms of current-carrying capacity for a single-phase and a three-phase 120 V system with effective load resistance of 15 Ω.

ingle-phase 8 A; three-phase 4 A

ingle-phase 32 A; three-phase 16 A

ingle-phase 16 A; three-phase 8 A

ingle-phase 8 A; three-phase 4 A

ingle-phase 16 A; three-phase 0 A

In a Y-connected source feeding a ∆-connected load,

Each phase of the load has a voltage across it equal to √3

Each phase of the load has one-third of the full line voltage across it

Each phase of the load has two-thirds of the full line voltage across it

Each phase of the load has the full line voltage across it

Each phase of the load has a voltage across it equal to √3

In a ∆-connected source driving a ∆-connected load, the

Load voltage and line voltage are one-third the source voltage for a given phase

Load voltage and line voltage are two-thirds the source voltage for a given phase

Load voltage and line voltage cancel for a given phase

Load voltage, line voltage, and source phase voltage are all equal for a given phase

In a ∆-connected source feeding a Y-connected load

Each phase voltage equals the corresponding load voltage

Each phase voltage equals the difference of the corresponding load voltages

Each phase voltage equals the corresponding load voltage

Each phase voltage is one-third the corresponding load voltage

Each phase voltage is 60° Ωut of phase with the corresponding load voltage

A constant load power means a uniform conversion of

Mechanical to electrical energy

Electrical to mechanical energy

In the transformer the function of a conservator is to

Provide fresh air for cooling the transformer

Supply cooling oil to transformer in time of need

Protect the transformer from damage when oil expends due to heating

A three-phase ∆-connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I θa = 12 ∠30° A, what are the polar expressions for the other phase currents?

I θb = 12 ∠120° A, I θc = 12 ∠30° A

I θb = 12 ∠150° A, I θc = 12 ∠-90° A

I θb = 12 ∠120° A, I θc = 12 ∠30° A

I θb = 12 ∠30° A, I θc = 12 ∠120° A

I θb = 12∠ 90° A, I θc = 12 ∠90° A

In a Y-connected circuit, the magnitude of each line current is

three times the corresponding phase current

equal to the corresponding phase current

Compare the total copper cross sections in terms of current-carrying capacity for a single-phase and a three-phase 120 V system with effective load resistance of 15 .

single-phase 8 A; three-phase 4 A

single-phase 32 A; three-phase 16 A

single-phase 16 A; three-phase 8 A

single-phase 8 A; three-phase 4 A

single-phase 16 A; three-phase 0 A

In a balanced three-phase load, each phase has

a power consumption equal to IL

In a -connected source driving a -connected load, the

load voltage and line voltage are one-third the source voltage for a given phase

load voltage and line voltage are two-thirds the source voltage for a given phase

load voltage and line voltage cancel for a given phase

load voltage, line voltage, and source phase voltage are all equal for a given phase

In a -connected source feeding a Y-connected load,

each phase voltage equals the corresponding load voltage

each phase voltage equals the difference of the corresponding load voltages

each phase voltage equals the corresponding load voltage

each phase voltage is one-third the corresponding load voltage

each phase voltage is 60¬∞ out of phase with the corresponding load voltage

In a Y-Y source/load configuration, the

phase current, the line current, and the load current are 120¬∞ out of phase

phase current, the line current, and the load current are all equal in each phase

phase current, the line current, and the load current are 120¬∞ out of phase

phase current and the line current are in phase, and both are 120¬∞ out of phase with the load current

line current and the load current are in phase, and both are out of phase with the phase current

43 + Mcqs in Three Phase Systems In Power Applications in Electrical Engineering Page 1 McqOptions

1.	The term squirrel-cage applies to a type of three-phase ac generator.
A.	True
B.	False
Answer» B. False

Discussion

2.	In a -connected generator, there is a 120° difference between each line current and the nearest phase current.
A.	True
B.	False
Answer» C.

Discussion

3.	A three-phase -connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I θa = 12 30° A, what are the polar expressions for the other phase currents?
A.	I θb = 12 150° A, I θc = 12–90° A
B.	I θb = 12120° A, I θc = 1230° A
C.	I θb = 1230° A, I θc = 12120° A
D.	I θb = 1290° A, I θc = 1290° A
Answer» B. I θb = 12120° A, I θc = 1230° A

Discussion

4.	A two-phase generator is connected to two 90 load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?
A.	1.33 A
B.	1.88 A
C.	2.66 A
D.	1.77 A
Answer» E.

Discussion

5.	A single-phase sinusoidal voltage of 120 V is connected to a 90 load. Current in the circuit is
A.	13.3 mA
B.	133 mA
C.	1.33 A
D.	6.2 A
Answer» D. 6.2 A

Discussion

6.	Compare the total copper cross sections in terms of current-carrying capacity for a single-phase and a three-phase 120 V system with effective load resistance of 15 Ω.
A.	ingle-phase 32 A; three-phase 16 A
B.	ingle-phase 16 A; three-phase 8 A
C.	ingle-phase 8 A; three-phase 4 A
D.	ingle-phase 16 A; three-phase 0 A
Answer» C. ingle-phase 8 A; three-phase 4 A

Discussion

7.	A three-phase generator is connected to three 90 Ω load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?
A.	A
B.	.33 A
C.	.99 A
D.	.66 A
Answer» B. .33 A

Discussion

8.	An alternator is an electromechanical ac generator.
A.	True
B.	False
Answer» C.

Discussion

9.	The stator is the rotating assembly in a generator or motor.
A.	True
B.	False
Answer» C.

Discussion

10.	In a Y-connected source feeding a ∆-connected load,
A.	Each phase of the load has one-third of the full line voltage across it
B.	Each phase of the load has two-thirds of the full line voltage across it
C.	Each phase of the load has the full line voltage across it
D.	Each phase of the load has a voltage across it equal to √3
Answer» D. Each phase of the load has a voltage across it equal to √3

Discussion

11.	A two-phase generator is connected to two 90 Ω load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?
A.	1.33 A
B.	1.88 A
C.	2.66 A
D.	1.77 A
Answer» E.

Discussion

12.	Power is measured in a three-phase load by using an ammeter.
A.	True
B.	False
Answer» C.

Discussion

13.	In a Y-connected generator, there is a 120° difference between each line voltage and the nearest phase voltage.
A.	True
B.	False
Answer» C.

Discussion

14.	In a ∆-connected generator, there is a 120° difference between each line current and the nearest phase current.
A.	True
B.	False
Answer» C.

Discussion

15.	In a ∆-connected generator, all of the phase voltages are
A.	Zero
B.	Equal in magnitude
C.	One-third of total
D.	One-sixth of total
Answer» C. One-third of total

Discussion

16.	The most common type of ac motor is the
A.	Single-phase induction motor
B.	Two-phase induction motor
C.	Three-phase induction motor
D.	Two-phase squirrel-cage motor
Answer» D. Two-phase squirrel-cage motor

Discussion

17.	In a ∆-connected source driving a ∆-connected load, the
A.	Load voltage and line voltage are one-third the source voltage for a given phase
B.	Load voltage and line voltage are two-thirds the source voltage for a given phase
C.	Load voltage and line voltage cancel for a given phase
D.	Load voltage, line voltage, and source phase voltage are all equal for a given phase
Answer» E.

Discussion

18.	In a ∆-connected source feeding a Y-connected load
A.	Each phase voltage equals the difference of the corresponding load voltages
B.	Each phase voltage equals the corresponding load voltage
C.	Each phase voltage is one-third the corresponding load voltage
D.	Each phase voltage is 60° Ωut of phase with the corresponding load voltage
Answer» B. Each phase voltage equals the corresponding load voltage

Discussion

19.	Polyphase is characterized by two or more sinusoidal voltages, each having a different phase angle.
A.	True
B.	False
Answer» B. False

Discussion

20.	A simple two-phase generator consists of two conductive loops separated by 90°, rotating in a magnetic field.
A.	True
B.	False
Answer» B. False

Discussion

21.	A simple three-phase generator consists of three conductive loops separated by 120°.
A.	True
B.	False
Answer» B. False

Discussion

22.	The term 'squirrel-cage' applies to a type of three-phase ac generator.
A.	True
B.	False
Answer» B. False

Discussion

23.	A single-phase sinusoidal voltage of 120 V is connected to a 90 Ω load. Current in the circuit is
A.	13.3 mA
B.	133 mA
C.	1.33 A
D.	6.2 A
Answer» D. 6.2 A

Discussion

24.	A constant load power means a uniform conversion of
A.	Mechanical to electrical energy
B.	Electrical to mechanical energy
C.	Current to voltage
D.	Voltage to current
Answer» C. Current to voltage

Discussion

25.	A balanced load is one in which all the impedances are equal.
A.	True
B.	False
Answer» B. False

Discussion

26.	In the transformer the function of a conservator is to
A.	Provide fresh air for cooling the transformer
B.	Supply cooling oil to transformer in time of need
C.	Protect the transformer from damage when oil expends due to heating
D.	None of the above
Answer» D. None of the above

Discussion

27.	A three-phase ∆-connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I θa = 12 ∠30° A, what are the polar expressions for the other phase currents?
A.	I θb = 12 ∠150° A, I θc = 12 ∠-90° A
B.	I θb = 12 ∠120° A, I θc = 12 ∠30° A
C.	I θb = 12 ∠30° A, I θc = 12 ∠120° A
D.	I θb = 12∠ 90° A, I θc = 12 ∠90° A
Answer» B. I θb = 12 ∠120° A, I θc = 12 ∠30° A

Discussion

28.	In a Y-connected circuit, the magnitude of each line current is
A.	one-third the phase current
B.	three times the corresponding phase current
C.	equal to the corresponding phase current
D.	zero
Answer» D. zero

Discussion

29.	Compare the total copper cross sections in terms of current-carrying capacity for a single-phase and a three-phase 120 V system with effective load resistance of 15 .
A.	single-phase 32 A; three-phase 16 A
B.	single-phase 16 A; three-phase 8 A
C.	single-phase 8 A; three-phase 4 A
D.	single-phase 16 A; three-phase 0 A
Answer» C. single-phase 8 A; three-phase 4 A

Discussion

30.	If in a Y-connected ac generator, each phase voltage has a magnitude of 90 VRMS, what is the magnitude of each line voltage?
A.	0 V
B.	90 V
C.	156 V
D.	180 V
Answer» D. 180 V

Discussion

31.	In a balanced three-phase load, each phase has
A.	an equal amount of power
B.	one-third of total power
C.	two-thirds of total power
D.	a power consumption equal to IL
Answer» B. one-third of total power

Discussion

32.	In a Y-connected circuit, between each line voltage and the nearest phase voltage, there is a phase angle of
A.	0¬∞
B.	30¬∞
C.	60¬∞
D.	120¬∞
Answer» C. 60¬∞

Discussion

33.	Polyphase generators produce simultaneous multiple sinusoidal voltages that are separated by
A.	certain constant phase angles
B.	certain constant frequencies
C.	certain constant voltages
D.	certain constant currents
Answer» B. certain constant frequencies

Discussion

34.	In a certain Y-Y system, the source phase currents each have a magnitude of 9 A. The magnitude of each load current for a balanced load condition is
A.	0.125
B.	0.25
C.	0.375
D.	27 A
Answer» D. 27 A

Discussion

35.	In a -connected source driving a -connected load, the
A.	load voltage and line voltage are one-third the source voltage for a given phase
B.	load voltage and line voltage are two-thirds the source voltage for a given phase
C.	load voltage and line voltage cancel for a given phase
D.	load voltage, line voltage, and source phase voltage are all equal for a given phase
Answer» E.

Discussion

36.	In a three-phase system, when the loads are perfectly balanced, the neutral current is
A.	zero
B.	one-third of maximum
C.	two-thirds of maximum
D.	at maximum
Answer» B. one-third of maximum

Discussion

37.	A three-phase generator is connected to three 90 load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?
A.	0
B.	1.33 A
C.	3.99 A
D.	2.66 A
Answer» B. 1.33 A

Discussion

38.	In a -connected generator, there is a 120¬∞ difference between each line current and the nearest phase current.
A.	1
B.
C.	1
D.
Answer» C. 1

Discussion

39.	In a -connected source feeding a Y-connected load,
A.	each phase voltage equals the difference of the corresponding load voltages
B.	each phase voltage equals the corresponding load voltage
C.	each phase voltage is one-third the corresponding load voltage
D.	each phase voltage is 60¬∞ out of phase with the corresponding load voltage
Answer» B. each phase voltage equals the corresponding load voltage

Discussion

40.	In a Y-Y source/load configuration, the
A.	phase current, the line current, and the load current are all equal in each phase
B.	phase current, the line current, and the load current are 120¬∞ out of phase
C.	phase current and the line current are in phase, and both are 120¬∞ out of phase with the load current
D.	line current and the load current are in phase, and both are out of phase with the phase current
Answer» B. phase current, the line current, and the load current are 120¬∞ out of phase

Discussion

41.	In a certain three-wire Y-connected generator, the phase voltages are 2 kV. The magnitudes of the line voltages are
A.	2,000 V
B.	6,000 V
C.	666 V
D.	3,464 V
Answer» E.

Discussion

42.	In a -connected generator, all of the phase voltages are
A.	zero
B.	equal in magnitude
C.	one-third of total
D.	one-sixth of total
Answer» C. one-third of total

Discussion

43.	In a three-phase system, the voltages are separated by
A.	45¬∞
B.	90¬∞
C.	120¬∞
D.	180¬∞
Answer» D. 180¬∞

Discussion

Explore topic-wise MCQs in Electrical Engineering.

The term squirrel-cage applies to a type of three-phase ac generator.

In a -connected generator, there is a 120° difference between each line current and the nearest phase current.

A three-phase -connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I θa = 12 30° A, what are the polar expressions for the other phase currents?

A two-phase generator is connected to two 90 load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?

A single-phase sinusoidal voltage of 120 V is connected to a 90 load. Current in the circuit is

Compare the total copper cross sections in terms of current-carrying capacity for a single-phase and a three-phase 120 V system with effective load resistance of 15 Ω.

A three-phase generator is connected to three 90 Ω load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?

An alternator is an electromechanical ac generator.

The stator is the rotating assembly in a generator or motor.

In a Y-connected source feeding a ∆-connected load,

A two-phase generator is connected to two 90 Ω load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?

Power is measured in a three-phase load by using an ammeter.

In a Y-connected generator, there is a 120° difference between each line voltage and the nearest phase voltage.

In a ∆-connected generator, there is a 120° difference between each line current and the nearest phase current.

In a ∆-connected generator, all of the phase voltages are

The most common type of ac motor is the

In a ∆-connected source driving a ∆-connected load, the

In a ∆-connected source feeding a Y-connected load

Polyphase is characterized by two or more sinusoidal voltages, each having a different phase angle.

A simple two-phase generator consists of two conductive loops separated by 90°, rotating in a magnetic field.

A simple three-phase generator consists of three conductive loops separated by 120°.

The term 'squirrel-cage' applies to a type of three-phase ac generator.

A single-phase sinusoidal voltage of 120 V is connected to a 90 Ω load. Current in the circuit is

A constant load power means a uniform conversion of

A balanced load is one in which all the impedances are equal.

In the transformer the function of a conservator is to

A three-phase ∆-connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I θa = 12 ∠30° A, what are the polar expressions for the other phase currents?

In a Y-connected circuit, the magnitude of each line current is

Compare the total copper cross sections in terms of current-carrying capacity for a single-phase and a three-phase 120 V system with effective load resistance of 15 .

If in a Y-connected ac generator, each phase voltage has a magnitude of 90 VRMS, what is the magnitude of each line voltage?

In a balanced three-phase load, each phase has

In a Y-connected circuit, between each line voltage and the nearest phase voltage, there is a phase angle of

Polyphase generators produce simultaneous multiple sinusoidal voltages that are separated by

In a certain Y-Y system, the source phase currents each have a magnitude of 9 A. The magnitude of each load current for a balanced load condition is

In a -connected source driving a -connected load, the

In a three-phase system, when the loads are perfectly balanced, the neutral current is

A three-phase generator is connected to three 90 load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?

In a -connected generator, there is a 120¬∞ difference between each line current and the nearest phase current.

In a -connected source feeding a Y-connected load,

In a Y-Y source/load configuration, the

In a certain three-wire Y-connected generator, the phase voltages are 2 kV. The magnitudes of the line voltages are

In a -connected generator, all of the phase voltages are

In a three-phase system, the voltages are separated by