Alternating Current Waveform

Before we learn more about this topic, let us quickly understand a few key terms.

• The time interval between a definite value of two successive cycles is the period.


• The number of cycles or number of periods per second is frequency.


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  The maximum value in both directions is the amplitude.
  


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  The normal waveform of AC in most of the circuits are sinusoidal in nature in which the positive half period corresponds with the positive direction of the current and vice-versa. In addition, a triangular or square wave can also be used to represent the alternating current waveform.

  
  

  Audio amplifiers that deal with analogue voice or music signals produce irregular AC waves. Some electronic oscillators produce square or sawtooth waves.

  
  Average Value of AC

  Average value is usually defined as the average of the instantaneous values of alternating current over a complete cycle. The positive half cycle of asymmetrical waves such as a sinusoidal voltage or current waveform will be equal to the negative half cycle. Which implies that the average value after the completion of a full cycle is equal to zero.

  
  

  Since, both the cycles do some work the average value is obtained by avoiding the signs. Therefore, the average value of alternating quantities of sinusoidal waves can be considered by taking the positive cycle only.

  
  RMS Value of AC Wave

  RMS value is defined as the square root of means of squares of instantaneous values. It can also be described as the amount of AC power that generates the same heating effect as an equivalent DC power.

  
  Phasor Diagrams

  The phasor diagram is used to determine the phase relationships between two or more sine waves propagating with the same frequency. Here, we use the terms “lead”, “lag” and also “in-phase”, “out-of-phase” to indicate the relation between one waveform with the other.

  
  

  Phasor diagrams will be of the form