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Module 4, Lesson 3 > ITEC 220 Test #3 > Flashcards

ITEC 220 Test #3 Flashcards

1
Q

Cycle

A

The complete sequence of values of a repetitive voltage or current

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2
Q

Waveform

A

A graph showing the variations of the voltage and current with respect to time

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3
Q

Period

A

The time of one complete cycle

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4
Q

Periodic waveform

A

A graph of a wave which repeats itself every period

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5
Q

Time duration (t)

A

The length of time needed to complete a cycle

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6
Q

Frequency

A

The number of cycles per unit of time

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7
Q

Hertz (Hz)

A

Unit of frequency measurement meaning cycles per second

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8
Q

Sinusoidal waveform

A

Any waveform that can be expressed as a sum of sine functions in respect to time

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9
Q

Alternation

A

A way of describing the state of a voltage or current which changes polarity periodically

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10
Q

Radian

A

Unit of angular measurement in which the arc of the angle on the circle is equal to the circles radius

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11
Q

Sine wave

A

A voltage or current whose waveform can be expressed by a single sine function in respect to time

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12
Q

Instantaneous voltage

A

The voltage present at a particular instant

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13
Q

Define the period as applied to an AC waveform

A

The time of one complete cycle

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14
Q

Define frequency as applied to an AC waveform

A

The number of cycles per unit of time

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15
Q

How man alternations are there in one cycle

A

2

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16
Q

How many radians are there in an angle of 180

A

3.14 (pi)

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17
Q

What is the peak value of a sine wave with a peak-to-peak voltage of 120 volts AC

A

60 HAC

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18
Q

What is the peak-to-peak value of a sine wave with a peak voltage of 120 volts AC

A

240 HAC

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19
Q

What is the average value (in volts) of a complete sine wave with equal amplitude positive and negative alternations

A

0

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20
Q

If the positive and negative alternations of a waveform are unequal in amplitude, is the waveform sinusoidal

A

No

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21
Q

AC voltages and currents are expressed in

A

RMS

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22
Q

The AC voltage of the power lines in our homes are rated for

A

110-120 volts

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23
Q

Average

A

Difference between the positive and negative peaks

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24
Q

The AC volts scale of a multimeter usually indicates

A

RMS voltages

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25
Q

Can an oscilloscope be used to measure RMS voltage and peak-to-peak voltage

A

Yes

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26
Q

Inductance

A

The property of a conductor that opposes a change in a circuit

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27
Q

Counter EMF

A

The effect that an inductor produces an opposing voltage to the applied voltage as the magnetic field changes with the applied voltage

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28
Q

Self-induction

A

Induction of an electromotive force in a coil by varying the current in the coil.

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29
Q

`Mutual induction

A

Induction of an electromotive force in a coil by a varying current in another coil which is magnetically coupled to the first coil

30
Q

Inductor

A

An electrical unit that exhibits inductance. Sometimes called a coil

31
Q

Henry

A

Basic unit of measure of inductance

32
Q

The letter symbol for inductance

33
Q

Reactance

A

An opposition of current flow in an AC current

34
Q

When AC is used, the voltage and current change

A

continuously

35
Q

The counter EMF developed across a coil, to which AC is applied is directly

A

Proportional to the frequency changes in AC voltages

36
Q

Inductive reactance

A

The opposition an inductor offers to current flow in an AC circuit

37
Q

Angular velocity

A

The rate for expressing a change in radians per unit of time. It is equal to 2(3.14)(f), where f is expressed in Hertz

38
Q

The counter EMF developed across a coil, to which AC is applied, is directly

A

Proportional to the inductance in a coil

39
Q

Inductive reactance of a coil is directly

A

Proportional to frequency to the inductance of the coil

40
Q

Phase angle

A

The angular difference between two waveforms

41
Q

Impedance

A

The vector sum of resistance and reactance

42
Q

Counter EMF is developed in a coil only when DC is applied, T or F

43
Q

Increasing the frequency of the AC source (increases, decreases) the counter EMF coil

44
Q

1 kilohertz equals

A

1000 hertz

45
Q

1 megahertz equals

A

1,000,000 hertz

46
Q

Current method

A

A method of calculating the impedance of a parallel circuit by first calculating the branch currents, adding the branch currents vectorially, and determining the impedance by Ohm’s law

47
Q

Mutual coupling

A

The interaction produced by two coils which share the same magnetic filed

48
Q

Mutual inductance

A

The inductance that modifies the total inductance of two coils which are connected together and share the same magnetic filed

49
Q

In a series RL circuit, the voltage must be added (arithmetically, vectorially)

A

Vectorially

50
Q

The impedance of a series RL circuit is less than the sum of R plus XL

51
Q

In a parallel circuit, what is the same in all components

52
Q

In parallel RL circuits, the resistance value is increases. How is total circuit current affected

A

The total current decreases

53
Q

What are the 2 applications of inductors

A
  1. Oppose changes of current through them 2. Inductive reactance is directly proportional to the frequency of the source voltage
54
Q

Transformer

A

An electrical device that transfers electrical energy from one circuit into another by electromagnetic induction

55
Q

Mutual coupling (transformers)

A

The method by which a changing current in one coil causes a voltage to be induced in another coil

56
Q

Primary winding

A

Portion of the transformer to which the input is applied

57
Q

Secondary winding

A

Portion of the transformer from which the output is obtained

58
Q

Why is soft iron preferred over steel as a core material

A

It does not retain magnetism

59
Q

Turns ratio

A

The ratio number of turns of the secondary winding divided by the number of turns of the primary winding

60
Q

More primary turns

A

Step-down transformer

61
Q

More secondary turns

A

Step-up transformer

62
Q

Eddy currents

A

Are currents that are produced by the voltages induced into the core of a transformer

63
Q

Hysteresis

A

The delay in magnetism caused by extra energy and time required to change the magnetization of the minute molecular magnets in the core

64
Q

Core loss

A

The total losses in the core due to eddy currents and hysteresis

65
Q

I2R loss

A

The loss of energy due to the resistance of the copper wire

66
Q

Transformer hum

A

The vibration caused by the movement of the plates of the transformer core

67
Q

Flux leakage

A

A loss of magnetic flux

68
Q

Core Saturation

A

A condition where the core will accept no more magnetic flux

69
Q

Copper losses in a transformer could be decreased by

A

A higher quality copper

70
Q

Laminating an iron core decreases what

A

Eddy current losses

71
Q

Why are transformers used in long-dsitance power transmissions systems

A

The applied voltages can be increased or decreased

72
Q

List several additional uses of transformers

A

Computers, cellphones, substances, and instrument transformers

Module 4, Lesson 3 (18 decks)

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