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Electrical theory > aC Electrical > Flashcards

aC Electrical Flashcards

0
Q

Three forms of AC?

A

Square wave, triangle tooth, sine wave.

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1
Q

What is alternating current ?

A

A form of current electricity where the polarity of the source periodically changes

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2
Q

Describe square wave?

A

Polarity periodically changes but value does not

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3
Q

Describe triangle tooth?

A

Polarity periodically changes, value changed with straight line variation.

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4
Q

Describe sine wave?

A

Polarity periodically changes, value changes based on sine function

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5
Q

Generation of sine AC?

A

Created through the principle of electromagnetic induction.

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6
Q

Definition of electromagnetic induction?

A

The creation of an electrical potential in a conductor by passing that conductor through lines of magnetic flux

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7
Q

What’s the difference between magnetic induction and electromagnetic induction?

A

Magnetic induction used an actual magnet

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8
Q

Polarity if the potential is based on what two things?

A

The orientation of the lines of flux, the direction the conductor is cutting the lines of flux.

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9
Q

How is the polarity of the potential determined?

A

By the left hand rule.

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10
Q

What is the left hand rule?

A

Point first finger in the direction of the lines of flux, point thumb in direction of conductor movement, middle finger will point in the direction of current flow.

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11
Q

Two ways of increasing potential?

A

Increase the strength of the flux field being cut, increase the rate at which the lines of flux are being cut.

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12
Q

Ways to increase the strength of the flux field?

A

Increase current flow through the electromagnet

Increase the density of the lines of flux

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13
Q

Ways to increase the rate at which lines of flux are cut?

A

Increase the speed of the conductor

Increase the number of conductors cutting the flux

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14
Q

Advantages of AC over DC?

A

Much easier to generate large quantities of, much easier to change values without substantial power loss, much easier to transfer over long distances.

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15
Q

Disadvantage of AC?

A

Not as efficient as DC.

16
Q

What is a cycle?

A

One complete sequence of events from zero to the negative peak and back to zero

17
Q

What is an alternation?

A

One half of a cycle, in either the positive or negative direction

18
Q

What is a period?

A

The time required for one cycle to occur, measured in seconds.

19
Q

What is frequency?

A

The number of cycles per second,

Measured in hertz.

20
Q

Important thing to remember about period and frequency?

A

The are inverses of each other.

21
Q

Formula for frequency?

A 
   120
22
Q

What is a phase?

A

The positional relationship between the current and voltage with respect to when each is increasing and decreasing.

23
Q

What is in phase?

A

An immediate increase in either current or voltage coincides with an immediate increase in the other

24
Q

What is out of phase?

A

Any condition other than in phase

25
Q

Phase shift?

A

The amount of current and voltage are out of phase, in degrees of conductor rotation.

26
Q

Lead or lag?

A

Tells which changes first, given with respect of current.

27
Q

What is the most out of phase something can be?

A

90°

28
Q

What is apparent power?

A

The amount of power that would be dissipated in a DC circuit, apparent power is not an actual power, it is measured in volt amps.

29
Q

Formula for apparent power?

A

P=IxE

30
Q

What is true power?

A

The amount of power actually dissipated in an AC circuit, the amount of power is determined by amount of phase shift

31
Q

What is true power measured in?

A

Watts

32
Q

What is power factor?

A

The ratio of true power to apparent power.

33
Q

Formula for power factor?

A

PF= Pt/Pa or Pt= pa x pf = I x E cos theta

34
Q

Peak value?

A

The maximum instantaneous measure of either current or voltage in either the positive or negative direction

35
Q

Peak to peak value?

A

The maximum difference between the positive peak and the negative peak

36
Q

Average value?

A

The average value of all instantaneous values in one alternation

37
Q

Formula for average value?

A

.707 peak value, also known as the root mean square

38
Q

Significance of effective value?

A

It is how we compare AC to DC, it is what we take as our source voltage, it is what we read on the multimeter

Electrical theory (6 decks)

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