Basic Definitions about the Alternating Quantity:

Here we take the instance of sinusoidal form of alternating current.

Figure: Sinusoidal Waveform

Cycle

It is the one complete set of positive & negative half of any alternating quantity.

Time Period

This is the time required in second to complete one cycle of any alternating quantity.

Frequency

Number of cycles per second is known as the frequency of alternating quantity. This is the reciprocal of the time period and its unit is cycle per second or Hertz.

                                                          f = 1/T (in Hertz)

In America and Japan it is 60 Hertz.

Amplitude

This is the peak or maximum value of the alternating quantity. In Figure, I_m indicate the amplitude of the current wave.