unit 16 alternating current - pbworks

Unit 16

Alternating Current

Unit 16 Alternating Current

Objectives:

• Discuss differences between direct and alternating current.

• Be able to compute instantaneous values of voltage and current for a sine wave.

• Be able to compute peak, RMS, and average values of voltage and current.

• Discuss the phase relationship or voltage and current in a pure resistive circuit.


• The single greatest advantage of

alternating current is that AC current can

be transformed and DC current cannot be

transformed.

• This allows high-voltage electrical power

to be distributed with smaller wires and

lower amperage.

• The electrical power is then transformed to

a lower voltage where it is needed.


Alternating current flows first in one direction

and then in the other direction.


A graph view of a square wave.


A square wave alternating current produced by a

switch and two batteries.


The sine wave is the most common of all the AC

wave forms.


The sine wave is produced by rotating machines.


One sine wave is 360 electrical degrees.


The voltage at any point along the sine wave is

equal to the maximum, or peak, value times the

sine of the angle of rotation.


As the loop approaches 90° of rotation, the flux

lines are cut at a faster rate.


E(INST) = E(MAX) x SINE θ

E(INST) = the voltage at any point on the

wave form

E(MAX) = the maximum, or peak, voltage

SINE θ = the sine of angle theta, the angle

of rotation


Instantaneous values of voltage along a sine wave.


Peak, Peak-to-Peak, and RMS values along a sine

wave.


RMS = Peak x 0.707

Peak = RMS x 1.414


In a pure resistive circuit, the voltage and current

are in phase.


Skin Effect – In an AC circuit, the electrons

are forced to the outside of the conductor.


Review:

1. Most of the electrical power generated in

the world is alternating current.

2. Alternating current can be transformed

and direct current cannot.

3. Alternating current reverses its direction

of flow at periodic intervals.


Review:

4. The most common AC wave form is the sine wave.

5. There are 360 degrees in one complete sine wave.

6. Sine waves are produced by rotating machines.


Review:

7. The instantaneous voltage at any point on a sine wave is equal to the peak, or maximum, voltage times the sine of the angle of rotation.

8. The peak-to-peak voltage is the amount of voltage attained by the wave form.

9. The peak value is the maximum amount of voltage attained by the wave form.


Review:

10.The current and voltage in a pure resistive

circuit are in phase with each other.

unit 16 alternating current - pbworks

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