Visual definitions of Vpeak,(max) VRMS,(Root Mean Square), period T and frequency f of a sinusoidal alternating signal.
We understand that the frequency is the number of periods per second. f = 1/T with T in seconds (s) and f in hertz (Hz).
The RMS voltage, for a sinusoidal one, is the average value of the rectified voltage.
AC current: Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction.
Alternating currents are accompanied (or caused) by alternating voltages. An AC voltage v can be described mathematically as a function of time by the following equation:
v(t) = Vpeak sin(ωt)
Period (T): length of time in seconds that the waveform takes to repeat itself from start to finish. This can also be called the Periodic Time of the waveform for sine waves.
Frequency (f): number of times the waveform repeats itself within a second.