aC Electrical

Question 0

Three forms of AC?

Answer 0

Square wave, triangle tooth, sine wave.

Question 1

What is alternating current ?

Answer 1

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

Question 2

Describe square wave?

Answer 2

Polarity periodically changes but value does not

Question 3

Describe triangle tooth?

Answer 3

Polarity periodically changes, value changed with straight line variation.

Question 4

Describe sine wave?

Answer 4

Polarity periodically changes, value changes based on sine function

Question 5

Generation of sine AC?

Answer 5

Created through the principle of electromagnetic induction.

Question 6

Definition of electromagnetic induction?

Answer 6

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

Question 7

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

Answer 7

Magnetic induction used an actual magnet

Question 8

Polarity if the potential is based on what two things?

Answer 8

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

Question 9

How is the polarity of the potential determined?

Answer 9

By the left hand rule.

Question 10

What is the left hand rule?

Answer 10

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.

Question 11

Two ways of increasing potential?

Answer 11

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

Question 12

Ways to increase the strength of the flux field?

Answer 12

Increase current flow through the electromagnet

Increase the density of the lines of flux

Question 13

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

Answer 13

Increase the speed of the conductor

Increase the number of conductors cutting the flux

Question 14

Advantages of AC over DC?

Answer 14

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

Question 15

Disadvantage of AC?

Answer 15

Not as efficient as DC.

Question 16

What is a cycle?

Answer 16

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

Question 17

What is an alternation?

Answer 17

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

Question 18

What is a period?

Answer 18

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

Question 19

What is frequency?

Answer 19

The number of cycles per second,

Measured in hertz.

Question 20

Important thing to remember about period and frequency?

Answer 20

The are inverses of each other.

Question 21

Formula for frequency?

Answer 21

   120

Question 22

What is a phase?

Answer 22

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

Question 23

What is in phase?

Answer 23

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

Question 24

What is out of phase?

Answer 24

Any condition other than in phase

Question 25

Phase shift?

Answer 25

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

Question 26

Lead or lag?

Answer 26

Tells which changes first, given with respect of current.

Question 27

What is the most out of phase something can be?

Answer 27

90°

Question 28

What is apparent power?

Answer 28

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.

Question 29

Formula for apparent power?

Answer 29

P=IxE

Question 30

What is true power?

Answer 30

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

Question 31

What is true power measured in?

Answer 31

Watts

Question 32

What is power factor?

Answer 32

The ratio of true power to apparent power.

Question 33

Formula for power factor?

Answer 33

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

Question 34

Peak value?

Answer 34

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

Question 35

Peak to peak value?

Answer 35

The maximum difference between the positive peak and the negative peak

Question 36

Average value?

Answer 36

The average value of all instantaneous values in one alternation

Question 37

Formula for average value?

Answer 37

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

Question 38

Significance of effective value?

Answer 38

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