i) Instantaneous value:

• The value of a particular quantity in an ac waveform at a particular instant of time is called as its instantaneous value

   

ii) Peak value:

• It is the maximum value that an ac quantity can take either during positive half cycle or negative half cycle.

   

iii)Time period for one cycle of alternating quantity: 

• The time taken by an alternating quantity to complete one full positive and negative half cycle is called as its time period.