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Difficulty: HardElectrical Current and Electron Flow

In a closed direct-current (DC) circuit operating under steady-state conditions, continuous electrical current requires a complete conducting loop through both the external load and the power source. Which of the following correctly describes the direction of physical electron movement throughout the complete circuit?

  1. A
    Electrons flow from the positive terminal to the negative terminal through the external load, and from the negative terminal to the positive terminal inside the power source.
  2. Electrons flow from the negative terminal to the positive terminal through the external load, and are driven from the positive terminal to the negative terminal inside the power source.Answer
  3. C
    Electrons circulate in a single uninterrupted direction from the negative terminal to the positive terminal through both the external conductor and inside the power source.
  4. D
    Electrons and conventional current both travel from the positive terminal to the negative terminal through the external load, driven directly by electromotive force.

Answer

Electrons flow from the negative terminal to the positive terminal through the external load, and are driven from the positive terminal to the negative terminal inside the power source.
In any direct-current circuit, free electrons in the external conductors drift from the negative terminal toward the positive terminal due to electrostatic forces. To sustain continuous current, the power source utilizes electromotive force to pump electrons internally from the positive terminal back to the negative terminal, completing the closed cycle.

Step-by-Step Solution

1
Analyze external electron movement
External drift is from the negative terminal to the positive terminal.
Free electrons in metallic conductors carry a negative electric charge and are repelled by the negative battery terminal and attracted toward the positive terminal.
2
Analyze closed-loop continuity inside the source
Internal drift is from the positive terminal to the negative terminal.
To maintain a continuous current without charge buildup, the source's electromotive force (chemical or mechanical energy) does work against the internal electric field to transport electrons from the positive terminal back to the negative terminal.
3
Synthesize full loop current dynamics
External flow is negative-to-positive; internal transport is positive-to-negative.
A complete electrical circuit forms a closed loop, ensuring conservation of electric charge across all nodes.

Key Concept

Closed-Loop Electron Drift and Charge Conservation in DC Circuits
Estimated Time:45s
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Topics

Electrical Current and Electron Flow

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