Circuit basics: A voltage source will actually drive current only when the electrical circuit is in which state?

Introduction / Context:
Understanding when voltage causes current to flow is foundational in circuit theory. Students often confuse the presence of voltage with actual charge movement. The key is whether a complete conducting path exists for electrons to move through the circuit elements and back to the source.

Given Data / Assumptions:

• Ideal voltage source connected to passive components such as resistors or loads.
• Room temperature and ordinary conductors.
• No exotic displacement currents; focus is on simple direct or low-frequency circuits.

Concept / Approach:
Ohm's law states I = V/R for a closed loop. Current requires a continuous loop to provide a path for charge carriers. An open circuit breaks the loop and results in zero current, even if voltage is present across the open terminals.

Step-by-Step Solution:
Recognize requirement: current flow needs a continuous conducting path.Apply Ohm's law: in a closed circuit with finite resistance, I = V/R is nonzero.Consider open circuit: R is effectively infinite; I approaches zero despite applied V.Assess distractions: insulation or high resistance reduces current magnitude but does not by itself enable flow without closure of the loop.

Verification / Alternative check:
Measurements with an ammeter show zero current when a switch is open and nonzero current once the switch is closed across the same source and load.

Why Other Options Are Wrong:
Open: path is broken; no sustained charge flow.Insulated from ground: circuits can operate without a ground reference; ground is not required for current in a closed loop.Very high resistance: current becomes very small, but still requires a closed path; high resistance does not define the condition for flow.

Common Pitfalls:
Equating the presence of voltage with current flow regardless of circuit continuity.Assuming ground is mandatory for any circuit to function.

Final Answer:
Closed (complete path)