Peak value is a term used in the context of alternating current (AC) and refers to the maximum value attained by an alternating quantity during one cycle. It is also known as the maximum value, amplitude, or crest value. The peak value of a sinusoidal alternating quantity is obtained at 90 degrees.

It is important to note that peak value is different from peak-to-peak value, which is the difference between the highest and lowest values in a waveform. In AC, the peak-to-peak value is twice the peak value or 2.828 times the root-mean-square (RMS) value. Peak-to-peak voltage is indicated by VPP.

In addition to peak value and peak-to-peak value, there are other terms used to describe AC waveforms, including average value and RMS value. The average value is the average of all the instantaneous values of an alternating voltage and current over one complete cycle. The RMS value is the actual value of an alternating quantity that tells us the energy transfer capability of an AC source. It is the square root of the mean of squares of instantaneous values. The ammeter records the RMS value of alternating current, and the voltmeter records the RMS value of alternating voltage.

In summary, peak value is the maximum value attained by an alternating quantity during one cycle, and it is different from peak-to-peak value. Average value and RMS value are other terms used to describe AC waveforms.