i) Instantaneous value: The instantaneous value is “the value of an alternating quantity (it may ac voltage or ac current or ac power) at a particular instant of time in the cycle”.
The value of alternating quantity (emf, voltage or current) at any particular instant is called the instantaneous value.
ii) Time Period:
The time (in sec) required by an alternating quantity to complete its one cycle is known as time period.
It is defined as the maximum or peak value attained by an alternating quantity during its positive or negative half cycle.
iv) Phase difference:
Phase difference is the difference in phase angle between two sinusoids or phasors.