FIGURE 64. MAXIMUM OR PEAK VALUE.

During each complete cycle of ac there are always two maximum or

peak values, one for the positive halfcycle and the other for

the negative halfcycle. The difference between the peak

positive value and the peak negative value is called the peak

topeak value of the sine wave. This value is twice the maximum

or peak value of the sine wave and is sometimes used for

measurement of ac voltages. Note the difference between peak

and peaktopeak values in figure 65 on the following page.

Usually alternating voltage and current are expressed in

EFFECTIVE VALUES rather than in peaktopeak values.

(2) *Instantaneous Value*. The INSTANTANEOUS value of an

alternating voltage or current is the value of voltage or

current at one particular instant. The value may be zero if the

particular instant is the time cycle at. which the polarity of

the voltage is changing. It may also be the same as the peak

value, if the selected instant, is the time in the cycle at

which the voltage or current stops increasing and starts

decreasing. There are actually an infinite number of

instantaneous values between zero and the peak value.

(3) *Average Value*. The AVERAGE value of an alternating

current or voltage is the average of ALL the INSTANTANEOUS

values during ONE alternation. Since the voltage increases from

zero to peak value and decreases back to zero during one

alternation, the average value must be some value