Which of the following best defines an electrical current?

• A. The flow of positive charges only
• B. The magnetic field in a conductor
• C. The rate of heat transfer
• D. The transfer of electrons from a negative to a positive charge throughout the length of a conductor.

Answer: (D)

Electrical current is the rate at which electric charges pass a point in a circuit. In metal conductors, the charge carriers are electrons, so current corresponds to electrons moving through the conductor. The statement describes electrons transferring from a negative region toward a positive region along the length of the conductor, which is exactly how charge moves to produce current. This captures the idea that current is a flow of charge, not limited to positive charges alone.

The other ideas don’t define current: the magnetic field is a byproduct of current, not the current itself; heat transfer is a different form of energy flow; and current isn’t defined as the flow of positive charges only, since electrons (negative charges) are the actual movers in many conductors.