The flow of electrons changes periodically indicates which type of current?

• A. Direct current
• B. Joule's law
• C. Ohm's law
• D. Alternating current

Answer: (D)

The flow of electrons changes periodically describes alternating current. When the current reverses direction in regular cycles driven by a voltage that oscillates back and forth, the electrons move back and forth rather than one constant direction. This oscillation is typically characterized by a frequency (measured in hertz), such as the common 50 or 60 Hz in power systems. Direct current, by contrast, holds electrons moving in one direction with a steady magnitude. The other two ideas—Joule's law and Ohm's law—describe relationships between quantities like heat, voltage, current, and resistance and can apply to both AC and DC, but they don’t define the current’s directionality.