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AC vs DC electrical signals

2014-11-03 21:31  
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The DC and AC abbreviations are used in many descriptions of electronic circuits to show us what type of current is used for the electronic device .To understand how to use these electrical signals you must know differences of AC vs DC electrical signals.
The DC is a abbreviation from the Direct Current , in other words a DC current is a current that keeps its direction of flow .
A DC electricity flowing in a constant direction  and possess a voltage with constant polarity. A DC electricity  is provided by a battery with definite positive and negative voltage at terminals .
The AC abbreviation is used for Alternating Current and is produced by generators that switch polarity , reversing positive – negative voltage over time .
An Alternating Current is a current that reverse its direction of flow .
In one cycle, an alternation starts at zero and  rises to a maximum positive level then returns to zero and rises to a maximum negative level and again returns to zero.

Bipolar transistor circuit diagramBipolar transistor symbol Bipolar transistor circuit diagramBipolar transistor symbol

The number of such cycles completed per second is termed the ac frequency.

As you can see in these image in a complete cycle are two alternations, one in the positive direction and one in the negative direction .

AC vs DC electrical signals voltage and current direction flow

The polarity of the voltage across the wire coils of the generator  reverses as the opposite poles of the rotating magnet pass by. Connected to a load, this reversing voltage polarity will create a reversing current direction in the circuit.

When an alternator produces AC voltage, the voltage switches polarity over time in a very particular manner.

The most common AC wave form is an sine sinusoidal  . In electrical circuits, angles are measured in either degrees or radians .A compete cycle ( a period)  ( two alternations ) of AC voltage is always 360 degrees  .

AC voltage sine wave

A more popular measure for describing the alternating rate of an AC voltage or current wave than period is the rate of that back-and-forth oscillation.

The number of completed sine waves cycles during in one second of time represents the unit of measurement for the frequency ( Hertz – Hz ) .For example the power line frequency is 60 Hz (in USA) or 50Hz (in Europe ) , which means that the power line AC voltage oscillate  with a rate of 60 complete

back-and-forth cycles every second in the United States of America and 50 complete cycles in Europe .

So you must to remind that the :

- AC produced by an electromechanical alternator follows the graphical shape of a sine wave

- one cycle of a wave is one complete evolution of its shape until the point that it is ready to repeat itself

- the period of a wave is the amount of time it takes to complete one cycle

- frequency is the number of complete cycles that a wave completes in a given amount of time.

- frequency = 1/(period in seconds)

The sine wave of the AC voltage it is not the only kind of the wave that exists and are commonly produced by AC circuits  . The wave form produced by an AC circuit can be : Square wave  ,Triangle wave or Sawtooth wave .

AC Square wave  ,Triangle wave and Sawtooth wave .