Which statement about a closed electric circuit is true?

• A. A circuit without any voltage source can still have current.
• B. A battery always produces no current in a circuit.
• C. An open circuit permits current to flow.
• D. A closed path along which electrons can flow ensures current can move.

Answer: (D)

Current is the flow of electrons, and it only happens when there is a complete, conducting path from the power source, through any devices, and back to the source. A closed circuit provides that unbroken loop, so a voltage source can push electrons around and establish a steady current. If the loop is broken (an open circuit), the path isn’t complete, and electrons can’t keep moving, so no sustained current flows. A battery doesn’t always produce no current—it supplies the push—but that push only results in current when the circuit is closed. So the statement that a closed path along which electrons can flow ensures current can move captures the essential condition for current to occur.