How does AC voltage differ from DC voltage?

AC voltage, or alternating current voltage, is characterized by its ability to change direction and vary in magnitude over time. This is in contrast to DC voltage, or direct current voltage, which maintains a constant polarity and remains consistent in voltage levels. The fluctuating nature of AC voltage allows it to be transmitted efficiently over long distances and to be easily converted to different voltages, which is why it is commonly used for household power supply.

Household circuits predominantly rely on AC voltage for a number of reasons, including its efficiency and compatibility with large-scale generators and transformers. This makes it essential for powering appliances, lighting, and other devices in homes. The variability of AC allows for the use of transformers that can step up or step down voltages, making AC a versatile choice for electrical distribution.

The other options do not accurately reflect the fundamental differences between AC and DC voltages. Therefore, the choice that highlights that AC voltage varies with time while DC voltage remains constant is the most accurate representation of these two types of electrical currents.