Basic electric circuits: what is the smallest number of distinct terminals (polarities) required to establish a current flow through a passive load?

Introduction / Context:
Current requires a driving force and a closed path. In lumped circuit theory, this driving force is a potential difference between two points. The question tests recognition that at least two distinct terminals are needed to define such a difference and complete a circuit for current to flow through a load.

Given Data / Assumptions:

• A passive load (e.g., resistor) needs a voltage applied across it.
• Voltage is defined as the difference in electric potential between two nodes.
• A closed loop is formed from a source terminal through the load back to the other source terminal.

Concept / Approach:
One point alone cannot define a voltage; we need two points to establish a potential difference. Once a source provides a positive and a negative terminal (or two nodes at different potentials), and a conductive path connects them through the load, charges can move and current flows according to Ohm’s law I = E / R. Extra terminals like “neutral” may exist in power systems, but they are not the fundamental minimum requirement for current in a simple DC circuit.

Step-by-Step Solution:

Verification / Alternative check:
Consider a single battery and a lamp: one wire from battery positive to the lamp, and one wire from lamp back to battery negative completes the circuit. Removing either path or terminal stops the current completely.

Why Other Options Are Wrong:

Common Pitfalls:
Thinking a single “ground” reference suffices; it still implies a second node relative to ground. Also confusing system wiring conventions with fundamental circuit requirements.

Final Answer:
Two — a negative terminal and a positive terminal