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Started on Thursday, 12 March 2015, 06:52 AM

Completed on Sunday, 22 March 2015, 08:38 AM

Time taken 10 days 1 hour

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Terminal voltage is defined as the voltage that is:

Select one:

a. Measured from armature to ground

b. Measured at the output of the generator

c. Delivered across the load

d. Induced in the armature conductors

e. Applied to the field windings

The correct answer is: Measured at the output of the generator

The induced voltage that acts to counter the applied voltage in a DC generator is alsoknown as:

Select one:

a. Counter­electromotive flux

b. Counter­electromotive force

c. Electromotive static field

d. Static field of flux

e. Counter­applied force

The correct answer is: Counter­electromotive force

The three conditions necessary to induce a DC voltage output are a conductor,__________, and __________.

Select one:

a. magnetic field, relative motion between the two

b. electrons, magnetic field

c. resistance, relative motion between the two

d. resistance, relative motion between the two

e. electrons, resistance

The correct answer is: magnetic field, relative motion between the two

For the following diagram of a DC generator, is the direction of rotation of theconductor clockwise or counter­clockwise?

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Select one:

a. clockwise

b. counter­clockwise

The correct answer is: clockwise

When the field strength of a DC generator is varied, adjustments are made in thegenerator's:

Select one:

a. terminal voltage

b. induced voltage

c. voltage input

d. copper losses

e. mechanical losses

The correct answer is: terminal voltage

Which of the following is NOT one of the four internal losses of a DC generator?

Select one:

a. Mechanical rotational losses

b. Field losses

c. Hysteresis losses

d. Copper losses

e. Eddy­current losses

The correct answer is: Field losses

The function of torque in a DC motor is to:

Select one:

a. Increase current usage in the motor.

b. Produce and maintain rotation of the motor.

c. Create a given amount of horsepower for the motor.

d. Create CEMF to prevent overspeed of the motor.

e. Control voltage usage of the motor.

The correct answer is: Produce and maintain rotation of the motor.

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Field current and the magnetic field size in a DC motor are related in that they are:

Select one:

a. inversely related.

b. dependent on speed.

c. opposite.

d. always controlled by terminal voltage.

e. proportional.

The correct answer is: proportional.

Varying the field resistance on a DC motor is nomally used to control the:

Select one:

a. armature current

b. motor speed

c. motor temperature

d. armature voltage

e. terminal voltage

The correct answer is: motor speed

In a DC motor, torque decreases as armature current:

Select one:

a. increases

b. multiplies

c. remains constant

d. decreases

e. reverses

The correct answer is: decreases

A rotating conductor passing through magnetic lines of flux producing a voltagedescribes:

Select one:

a. an AC circuit

b. power use in a DC motor

c. a transformer

d. a simple AC generator

The correct answer is: a simple AC generator

The effective value of AC current produces __________ heat effect comparing to anequal value of DC current.

Select one:

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a. more

b. less

c. the same

The correct answer is: the same

The result of one side of the AC generator loop cutting lines of force producing apositive current in the first half cycle of rotation and a negative current in the secondhalf cycle explains:

Select one:

a. the frequency relative to DC

b. the root mean square theory

c. the effective value of AC current

d. the phase differential of AC

e. the development of a sine­wave output

The correct answer is: the development of a sine­wave output

Which best defines the effective value of an AC current relative to DC current, Wheresquare root of 3 = SQRT (3)

Select one:

a. Produces the same heating effect as the SQRT (3) times the amount of DCcurrent.

b. Produces SQRT (3) times the heating effect as an equal amount of DC current.

c. Produces the same heating effect as an equal amount of DC current.

d. Produces the same heating effect as 0.707 times the amount of DC current.

e. Produces twice the heating effect as an equal amount of DC current.

The correct answer is: Produces the same heating effect as an equal amount of DCcurrent.

Inductors cause an opposition to current flow in an AC current and is known as:

Select one:

a. inductive reactance

b. inductive resistance

c. reactive inductance

d. inductive capacitance

e. inductive resonance

The correct answer is: inductive reactance

Inductors cause an opposition to current flow in an AC circuit and is known as:

Select one:

a. inductive resistance

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b. reactive inductance

c. inductive resonance

d. inductive capacitance

e. inductive reactance

The correct answer is: inductive reactance

IF a series R­C­L AC circuit is at resonance, then:

Select one:

a. net reactance is high; current output is high.

b. net reactance is infinite; current output is high.

c. net reactance is zero; current output is determined by circuit resistance.

d. net reactance is zero; current output is determined by inductive reactance.

e. net reactance is high; current output is near zero.

The correct answer is: net reactance is zero; current output is determined by circuitresistance.

In a delta­connected generator:

Select one:

a. one side of the armature windings are connected to the same point.

b. each phase carries 57.7% of line voltage and is used for high voltage generation.

c. phase impedance does not have to be equal.

d. the three armature windings are connected in parallel.

e. the three armature winding are connected in series.

The correct answer is: the three armature winding are connected in series.

What kind of circuit would have its impedance infinite (high) and current at a minimumvalue?

Select one:

a. An open R­C­L AC circuit.

b. A series R­C­L AC circuit in resonance.

c. A series R­C­L AC circuit not at resonance.

d. A parallel R­C­L AC circuit at resonance.

e. A parallel R­C­L AC circuit not at resonance.

The correct answer is: A parallel R­C­L AC circuit at resonance.

In a purely inductive AC circuit [ __________ ] leads [ __________ ] by 90 degrees.

Select one:

a. voltage / current

b. current / voltage

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The correct answer is: voltage / current

Opposition to the flow of AC current caused by a capacitor is defined as:

Select one:

a. capacitive reactance

b. capacitive resistance

c. capacitive inductance

d. captive resonance

e. capacitive reluctance

The correct answer is: capacitive reactance

Current __________ voltage in a purely capacitive AC circuit by __________degrees.

Select one:

a. leads, 180

b. lags, 90

c. leads, 45

d. lags, 45

e. leads, 90

The correct answer is: leads, 90

Impedance is:

Select one:

a. the reaction of current to resistive components

b. the opposition to current flow caused by resistance

c. the total opposition to current flow in an AC circuit

d. the parallel relationship of voltage and current in a series circuit

e. the mathematical representation of voltage development.

The correct answer is: the total opposition to current flow in an AC circuit

The formula required to calculate the total current in a simple parallel R­C­L AC circuitis. (chose from a to e)

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Question 27Incorrect

Select one:

1. a

2. b.

3. c.

4. d.

5. e.

The correct answer is: d.

The state in which inductive reactance equals capacitive reactance (XL = XC) at aspecified frequency of alternating current is called:

Select one:

a. equilibrium

b. resistance

c. resonance

d. impedance

e. resolution

The correct answer is: resonance

If the net reactance is zero and current output is determined by circuit resistance for acircuit, then we have which of the following?

Select one:

a. A series R­C­L AC circuit not at resonance

b. A parallel R­C­L AC circuit not at resonance.

c. A series R­C­L AC circuit at resonance

d. An open R­C­L AC circuit.

e. A parallel R­C­L AC circuit at resonance.

The correct answer is: A series R­C­L AC circuit at resonance

For a parallel R­C­L circuit at resonance, the circuit output relative to current (I) wouldbe such that:

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Select one:

a. impedance low: current output is high

b. impedance infinite (high): current is at maximum value.

c. reactance equals resistance: current is high

d. impedance near zero: current is low

The correct answer is: impedance infinite (high): current is at maximum value.

What is an indication of an unbalanced load in a three­phase system?

Select one:

a. Abnormally low EMF in one of the phases

b. Abnormally low power factor in one of the phases

c. Abnormally high current in one of the phases

d. Abnormally high EMF in one of the phases

e. Abnormally high resistance in one of the phases

The correct answer is: Abnormally high current in one of the phases

The ratio between true power and apparent power defines the term:

Select one:

a. reflective factor.

b. motive factor.

c. corrective factor.

d. apparent factor.

e. power factor.

The correct answer is: power factor.

In an inductive AC circuit, the power factor __________ when voltage leads current.

Select one:

a. leading

b. lagging

The correct answer is: lagging

Which is a reason why three­phase power systems are used instead of single­phasepower systems in industry?

Select one:

a. Three­phase systems have lower power ratings.

b. Three­phase systems have a lower resistance

c. Three­phase systems are smaller in size

d. Three­phase systems provide a single voltage

e. Three­phase systems operate at higher voltage

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The correct answer is: Three­phase systems are smaller in size

Which is a reason why three­phase power systems are used instead of single­phasepower systems in industry?

Select one:

a. Three­phase systems provide a single voltage.

b. Three­phase systems operate at higher voltages.

c. Three­phase systems of equal size have higher power ratings.

d. Three­phase systems are larger in size.

Three­phase systems have a lower resistance.

The correct answer is: Three­phase systems of equal size have higher power ratings.

An indication of an unbalanced load in a three­phase system is an abnormally:

Select one:

a. High voltage in one of the phases

b. Low resistance in one of the phases

c. High current in one of the phases

d. Low power factor in one of the phases

e. High resistance in one of the phases

The correct answer is: High current in one of the phases

In the diagram below, phase 2 lags phase 1 by 60 degrees.

Chose 1 or 2

phase 2 lags phase 1 by 60 degrees

Power factor is defined as the ratio between ____________power and ________power

Select one:

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a. true, apparent

b. apparent, true

The correct answer is: true, apparent

AC generator power ratings are based on:

Select one:

a. the total voltage and current capacity for each pole of the generator.

b. the insulation rating of the windings of the generator.

c. the size of the prime mover and the maximum speed of the generator.

d. generator speed when developing the maximum current output.

e. the ability of the prime mover to overcome generator losses and dissipate heat.

The correct answer is: the ability of the prime mover to overcome generator losses anddissipate heat.

Placing two generators in parallel with a mismatch in frequency will result in:

Select one:

a. high current surges until frequency matches.

b. large opposing voltages and a decrease in output current.

c. the generator with the lower frequency being picked up as a real load.

d. the generator with the lower frequency being picked up as a reactive load.

e. a lowering of system frequency by the difference of the two generators.

The correct answer is: the generator with the lower frequency being picked up as a realload.

Placing two generators in parallel with a mismatch in frequency will result in:

Select one:

a. the generator with the lower frequency being picked up as a real load.

b. high current surges until frequency matches.

c. a lowering of system frequency by difference of the two generators.

d. large opposing voltages and a decrease in output current.

e. the generator with the lower frequency being picked up as a reactive load.

The correct answer is: the generator with the lower frequency being picked up as a realload.

Choose the letter corresponding to the statement that best describes the differencebetween a rotating field stationary armature AC generator and a stationary fieldrotating armature AC generator.

Select one:

a. The rotating field generator output is connected to the load without movingcontacts. The stationary field generator output can be interrupted because of worn or

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dirty moving contacts.

b. Much higher voltages and currents can be generated in the stationary fieldgenerator. The rotating armature generator is best suited for small loads.

c. The rotating field generator uses slip rings and brushes to convey the output. Thestationary field generator uses slip rings and brushes to convey the armature current.

d. In the rotating field generator, the slip ring and brush assembly is in series withthe load vs. parallel for the stationary field generator.

e. The rotating field generator produces higher current levels. The stationary fieldgenerator produces higher voltage levels.

The correct answer is: The rotating field generator output is connected to the loadwithout moving contacts. The stationary field generator output can be interruptedbecause of worn or dirty moving contacts.

A major advantage of wye­connected generator is:

Select one:

a. it provides an increase in current with no increase in voltage.

b. if one phase is damaged, the remaining two can deliver 3 phase power.

c. the impedance of the three phase windings do not have to be equal.

d. each phase carries 57.7% of line voltage and is used for high voltage generation.

e. the hysteresis losses of the generator are reduced by 57.7%.

If one phase is damaged, the remaining two can deliver 3 phase power.

The correct answer is: each phase carries 57.7% of line voltage and is used for highvoltage generation.

Match the correct component and purpose.

Part of an AC generator in which voltage is produced Armature

Part that is stationary Stator

Component used to drive the generator Prime Mover

Used to transfer power to or from the rotor Slip rings

Uses exciter voltage to produce magnetic flux Field

The correct answer is: Part of an AC generator in which voltage is produced – Armature,Part that is stationary – Stator, Component used to drive the generator – Prime Mover,Used to transfer power to or from the rotor – Slip rings, Uses exciter voltage toproduce magnetic flux – Field

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