Question

which best compares ac and dc?
ac flows in one direction, and dc repeatedly switches direction.
dc flows in one direction, and ac repeatedly switches direction.
ac is used only in generators, and dc is used only in motors.
dc is used only in generators, and ac is used only in motors.

Explanation:

To compare AC (Alternating Current) and DC (Direct Current), we recall their definitions: DC has a constant direction of current flow, while AC's current direction reverses periodically. Let's analyze each option:

• First option: Incorrect. AC switches direction, DC flows in one direction.
• Second option: Correct. DC flows in one direction, AC repeatedly switches direction.
• Third option: Incorrect. Both AC and DC are used in generators and motors (e.g., AC generators, DC motors, and also AC motors, DC generators exist).
• Fourth option: Incorrect. Same reasoning as third option—usage is not limited as stated.

Answer:

B. DC flows in one direction, and AC repeatedly switches direction.