In the single-phase system, an alternating voltage U, represented by volt, is produced and applied between two wires, where the load is connected, which will suck a current I, represented by the amp.
We must indicate some quantities so that the voltage and current waves do not remain in phase, that is, they do not go through the zero value at the same time, even if it has the same frequency, which happens for different types of loads, as the windings of electric motors, which, for example, are reactive loads. Boston Gear 2SC75
The frequency is in the number of times per second that the voltage changes direction and returns to the initial condition. A very important factor that must be checked refers to the maximum voltage, which is the peak value of the voltage. This means that the highest value reached by the voltage throughout the cycle, considering that this value is reached twice per cycle, once positive and once negative.
Thus, alternating current is characterized by the fact that the voltage, instead of remaining fixed, as between the poles of a battery, for example, varies according to time, alternately changing the direction.