Waveform of Alternating Quantity

Waveform:

     A shape formed by plotting instantaneous values of voltage or current as ordinate (y-axis) against time as abscissa(x-axis) is called waveform. 

Instantaneous Value:

    The value of alternating quantity at any instant is called instantaneous value.E.g., in above graph v=0 at t=0.

Cycle: 

    One complete set of positive and negative values of an alternating quantity.

—1 cycle = 360° or 2Π  

Cycle is shown as below.

Alternation:

Half cycle is called one alternation.

1 alternation =180° or Π .

 Alternation is shown as below.

Time Period:

     Time required to complete one cycle is called time period.It is represented by T. 

Frequency: 

     The literal meaning of frequency is repetition.In alternating quantity terminology it is defined as         "Number of times alternating voltage or current cycles  are formed on graph in one second is called  frequency."

 

The unit of frequency is cycles per second or Hz.

Amplitude:

    The maximum or highest value which is attained by an alternating voltage or current on the x-axis over the cycle is called amplitude.Note that it is without sign but if we say positive amplitude it means value attained in positive alternation often called positive peak value. In the same way negative peak value is also found in the negative half cycle.