What is the difference between AC and DC current.

a. AC current flows in one direction only, while DC current flows in both directions.
b. AC current changes direction periodically, while DC current flows in one direction only.
c. AC current flows at a higher voltage than DC current.
d. AC current is only used in residential applications, while DC current is only used in industrial applications.
Answer: b. AC current changes direction periodically, while DC current flows in one direction only.