Final answer:
An electrical current flowing first in one direction and then in the opposite direction is called Alternating Current (AC), which varies in magnitude and periodically reverses direction.
Step-by-step explanation:
An electrical current that flows first in one direction and then in the opposite direction is called Alternating Current (AC). Direct current (DC), on the other hand, refers to the flow of electric charge in only one direction. Alternating current (AC) differs as it is the flow of electric charge that periodically reverses direction, commonly used in residential and commercial power supplies, signaling a time-varying voltage source. The magnitude of alternating current changes at regular intervals of time, unlike DC's constant magnitude.