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Difficulty: MediumDirect Current (DC) vs. Alternating Current (AC)

Which of the following statements correctly describes how charge carrier (electron) movement differs between an alternating current (AC) circuit and a direct current (DC) circuit?

  1. A
    Electrons in an AC circuit flow continuously in one direction at twice the speed of electrons in a DC circuit.
  2. Electrons in an AC circuit oscillate back and forth periodically, whereas electrons in a DC circuit drift continuously in a single direction.Answer
  3. C
    Electrons in an AC circuit flow from the positive terminal to the negative terminal, whereas in a DC circuit they flow from negative to positive.
  4. D
    Electrons in an AC circuit lose and regain their negative charge periodically, whereas electrons in a DC circuit maintain constant voltage.

Answer

Electrons in an AC circuit oscillate back and forth periodically, whereas electrons in a DC circuit drift continuously in a single direction.
In direct current (DC), the electromotive force maintains a constant polarity, causing charge carriers (electrons) to drift steadily in one direction along the conductor. In alternating current (AC), the polarity of the voltage source reverses periodically at a given frequency, causing the electrons to oscillate rapidly back and forth around relatively fixed positions without traveling continuously from one end to the other.

Step-by-Step Solution

1
Identify the fundamental physical behavior of electric charge in Direct Current (DC).
In a DC circuit, a constant voltage polarity creates an electric field that causes electrons to drift steadily in one continuous direction.
Direct current is characterized by unidirectional flow over time.
2
Identify the fundamental physical behavior of electric charge in Alternating Current (AC).
In an AC circuit, the source voltage periodically reverses polarity, causing the electric field to reverse direction and the electrons to oscillate back and forth in place.
Alternating current changes direction at a specific frequency (e.g., 60 Hz60\text{ Hz}), resulting in zero net displacement over complete cycles.

Key Concept

Direct Current (DC) involves unidirectional electron drift, while Alternating Current (AC) involves periodic bidirectional oscillation of electrons.
Estimated Time:45s
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Topics

Direct Current (DC) vs. Alternating Current (AC)

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