AgTM 330 tests 1 and 2 toolbox
A delta connected set of windings has a phase voltage of 100 V. The line voltage is _____.
100 V
The horsepower rating of three-phase motors and the kilovolt-ampere rating of three-phase transformers are about _____ greater than for single-phase motors or transformers with a similar frame size.
150%
A delta-connected set of windings has a phase current of 10 A. The line current is _____.
17.32 A
_____ operate on the same principle of electromagnetic induction as DC generators, but they have no commutator.
Alternators
The _____ ride against the commutator segments and are used to connect the armature to the external circuit of the DC machine.
Brushes
The transformer that converts a high voltage from the power company down to 240/120 V for homes and businesses is called a(n) _____ transformer.
Distribution
Magnetic lines of force are called _____.
Flux
When using the left-hand generator rule, the center finger points to the direction of _____.
Flux
In the English system of measure, magnetic strength is measured in a term called _____."
Flux density
In three-phase power systems, the delivered power _____.
Never falls to zero
Square waves are generally produced by electronic devices called _____.
Oscillators
The maximum point of a waveform is called the _____.
Peak
When a magnetic materials molecules are all lined up, and increases in current flow no longer cause increases in magnetic field strength, the material has reached _____.
Saturation
The transformer winding, which is the output winding, is called the _____ winding.
Secondary
The series generator has only a series field, which is connected in _____ with the armature.
Series
Connection to the armature of an alternator is normally done by using _____.
Slipring
When using the left-hand generator rule, the thumb points to the direction of _____.
Thrust
The magnetically operated device that can change values of voltage, current, and impedance without changing frequency is the _____.
Transformer
A series motor may be operated with no load connected.
True
A triangle wave is waveform in which voltage rises at a constant rate with respect to time.
True
In a three-phase circuit, the true power (watts) is found by _____.
multiplying apparent power by the power factor
The amount of magnetism left in a material after the magnetizing force has stopped is called _____.
residual magnetism
If a voltage is being induced into a conductor by electromagnetic induction, reversing the direction of motion of the conductor will _____.
reverse the polarity of the induced voltage
The amplitude of a waveform is measured from _____.
zero to the highest value obtained in either direction
Often in calculations of values in three-phase systems, the square root of three occurs. The approximate value of this constant is _____.
1.732
If the peak-to-peak voltage is 240V the peak voltage is
120 V
Three-phase voltages are _____ out of phase with each other.
120 degrees
A transformer has a 240 V primary and a 60 V secondary. With a 5 ohm load connected, what is the primary current?
3 A
A transformer has a 240 V primary and a 120 V secondary. With a 30 ohm load connected, what is the primary volt-amps?
480
A delta connected set of windings has a phase voltage of 480 V. What is the value of the line voltage?
480 V
A transformer has a 2:1 turns ratio. 120 V is applied to the primary. What is the secondary voltage?
60 V
In a balanced three-phase system, the conductors need be only about _____ the size of conductors for a single-phase, two-wire system of the same kilovolt-ampere (kVA) rating.
75%
The rotating part of a generator is called the _____.
Armature
The speed regulation of a DC motor is proportional to the _____.
Armature resistance
In a compound DC motor control circuit, the field loss relay will disconnect the _____ if power is lost to the _____.
Armature, shunt field
A basic law of magnetism states that unlike poles _____ and like poles _____.
Attract, repel.
A transformer that has one winding, which is used for both the primary and secondary, is called a(n) _____.
Autotransformer
Electrons can form spin patterns that _____ the magnetic field of the material.
Cancel
The component of a DC generator that converts the armature AC into DC is the _____.
Commutator
A generator containing both series and shunt fields is called a _____ generator.
Compound
The relationship of the strengths of the two fields in a generator determines the amount of _____.
Compounding
Each complete waveform of 360° is called a _____.
Cycle
The angular difference between true north and magnetic north is known as the angle of _____.
Declination
Line voltage and phase voltage are the same in the _____ connection.
Delta
The three-phase connection in which three separate inductive loads have been connected together is the _____ connection.
Delta
If an object is placed in the field of an strong electromagnet connected to an AC line, the object will be _____.
Demagnetized
The compound motor connection that should generally be avoided is the _____.
Differential
When a conductor cuts magnetic lines of force, a voltage is induced into the conductor. This principle is called _____.
Electromagnetic induction
A magnet that produces a magnetic field as long as current is flowing is called a(n) _____ magnet.
Electromagnets
Magnetism can be explained in terms of _____ spin patterns.
Electrons
In a transformer, even when there is no load connected, there will be some small current flow known as _____ current.
Excitation
A device that converts mechanical energy into DC electrical energy is a(n) _____.
Generator
The unit of frequency is _____.
Hertz
Permanent magnet motors have _____ efficiency than conventional field-wound motors.
Higher
When current rises and falls at the same rate as the voltage and reverses the direction of flow when the voltage reverses polarity, the current is said to be _____ with the voltage.
In phase
The three substances that form natural magnets are _____.
Iron, nickel, and cobalt.
A transformer in which the primary and secondary are physically separated and not connected by a conductor is called a(n) _____ transformer.
Isolation
A way of determining the relationships of the motion of the conductor, the magnetic field direction, and the direction of the induced current is by using the _____.
Left-hand generator rule
A wave in which the voltage rises at a constant rate with respect to time is a _____ wave.
Linear
Man-made permanent magnets retain their magnetism _____ than natural magnets.
Longer
Lodestone is a name for a naturally occurring magnetic material that is also called _____.
Magnetite
Shunt field windings are connected in parallel with the armature. They are wound with _____ turns of fairly _____ wire.
Many, small
A device that converts electrical energy into mechanical energy is called a(n) _____.
Motor
If one alternator does not produce sufficient power to supply a load, another alternator can be connected to the circuit. The second alternator is connected in _____.
Parallel
Shunt generators contain only a shunt field winding connected in _____ with the armature.
Parallel
_____ do not require any power of force to maintain their field.
Permanent magnets
The measure of a material's ability to be magnetized is called _____.
Permeability
_____ provide(s) the magnetic field necessary for the operation of the machine.
Pole pieces
The transformer winding, which is the power input winding, is called the _____ winding.
Primary
The time required for current in an inductor to reach its full Ohm's law value is called the _____ time constant.
R-L
The measure of a material's resistance to magnetism is _____.
Reluctance
A(n) _____ load contains pure resistance.
Resistive
A compound motor has _____ field windings.
Series and shunts
The DC motor, known as a "constant speed motor," is the _____ motor.
Shunt
When the field winding of a DC motor is connected in parallel with the armature, the motor is called a _____ motor.
Shunt
When a motor is connected differential compound, the _____ determines the direction of rotation of the motor at no load or light load.
Shunt field
Rotating machines normally produce a waveform called a _____ wave.
Sine
The most common of all AC waveforms is the _____ wave.
Sine
The north magnetic pole of a compass needle is attracted to the _____ magnetic pole of the earth.
South
A transformer in which the secondary voltage is less than the primary voltage is called a(n) _____ transformer.
Step-down
A transformer in which the secondary voltage is more than the primary voltage is called a(n) _____ transformer.
Step-up
An isolation transformer has the same input and output voltages.
True
Counter-electromotive force (CEMF) and back-EMF are names for the voltage induced into the armature of a DC motor.
True
Earth contains magnetic poles.
True
If current is flowing in a circuit containing an inductor and the power switch is opened, the magnetic filed surrounding the inductor collapses and induces voltage into the inductor, resulting in a voltage spike.
True
The amount of voltage induced into a conductor depends on the turns of wire, the strength of the magnetic field, and the speed of cutting action.
True
The north pole of a compass needle points in the direction of the south geographic pole.
True
The unit of measure of the power delivered to the load in a DC circuit is _____.
Watts
Line current and phase current are the same in the _____ configuration.
Wye
The strength of an electromagnet is primarily proportional to its _____.
ampere-turns
_______________ materials are either metal or nonmetal materials that cannot be magnetized.
diamagnetic
_______________ materials are metals that are easily magnetized.
ferromagnetic
To locate the north pole of an electromagnet, use the _____ hand rule.
left
Series field windings are connected in series with the armature. They are wound with _____ turns of fairly _____ wire.
Few, large
The output voltage of a generator is usually controlled by the amount of _____.
Field excitation current
The direction of induced current can be determined by using the _____ left-hand generator rule.
Fleming
The number of cycles completed in one second is called a _____.
Frequency
_____ is the square root of the mean of the square of the instantaneous currents.
RMS
The_____ effect occurs when AC induces eddy currents into the conductor, which cause the electrons to be repelled toward the outer surface of the conductor.
Skin
In a transformer, the turns of primary wire compared to the turns of secondary wire is called the _____ ratio.
Turns