Unit 16 Alternating Current
Unit 16
Alternating Current
Alternating current flows first in one direction
and then in the other direction.
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.
Unit 16 Alternating Current
●
●
●
Unit 16 Alternating Current
A graph view of a square wave.
Unit 16 Alternating Current
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.
A square wave alternating current produced by a
switch and two batteries.
Unit 16 Alternating Current
The sine wave is the most common of all the AC
wave forms.
Unit 16 Alternating Current
The sine wave is produced by rotating machines.
Unit 16 Alternating Current
Unit 16 Alternating Current
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.
Unit 16 Alternating Current
As the loop approaches 90° of rotation, the flux
lines are cut at a faster rate.
Unit 16 Alternating Current
E(INST) = E(MAX) x SINE θ
One sine wave is 360 electrical degrees.
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
Unit 16 Alternating Current
Instantaneous values of voltage along a sine wave.
Unit 16 Alternating Current
Peak, Peak-to-Peak, and RMS values along a sine
wave.
Unit 16 Alternating Current
Unit 16 Alternating Current
In a pure resistive circuit, the voltage and current
are in phase.
Unit 16 Alternating Current
Skin Effect – In an AC circuit, the electrons
are forced to the outside of the conductor.
Unit 16 Alternating Current
Review:
RMS = Peak x 0.707
Peak = RMS x 1.414
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.
Unit 16 Alternating Current
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 .
Unit 16 Alternating Current
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.
Unit 16 Alternating Current
Review:
10. The current and voltage in a pure resistive
circuit are in phase with each other.