Final answer:
Alternating Current (AC) is the type of current that changes direction many times in a given period, unlike Direct Current (DC) which flows continuously in one direction.
Step-by-step explanation:
The current that changes direction many times in a given period is known as Alternating Current (AC). This is in contrast to Direct Current (DC), which flows in one direction continuously. Alternating current is the type of electric current that periodically reverses direction, as it does in the AC power supply to residential and commercial buildings.
Unlike direct current, whose magnitude is fixed, the magnitude of alternating current changes at regular intervals of time, often sinusoidally. Therefore, for electrical systems where the source voltage varies periodically, especially in a sinusoidal manner, alternating current is used.