Faults in series circuits: Does a short circuit in a series path prevent current flow? Analyze the effect of an unintended short (near-zero resistance connection) placed in series with other elements powered by a DC source.

Difficulty: Easy

Correct Answer: False

Explanation:


Introduction / Context:
Mistaking the effect of a short in a series circuit is common. This question checks whether learners understand that a short generally lowers resistance and increases current, rather than preventing it.


Given Data / Assumptions:

  • DC steady-state operation.
  • An “ideal short” means resistance approaching zero.
  • Components are in series unless a fault bridges across something.


Concept / Approach:

In series networks, total resistance RT is the sum of element resistances. Introducing a short as a replacement for a series element reduces that element’s resistance to approximately zero, thus lowering RT and increasing current. A condition that truly prevents current is an open circuit (infinite resistance), not a short (near-zero resistance).


Step-by-Step Solution:

Model the shorted element: Rshort ≈ 0 Ω.Compute total resistance: RT_new = R1 + 0 + R3 + ... ≤ RT_old.Current with Ohm’s law: I_new = V / RT_new ≥ V / RT_old.Thus, current is not prevented; it usually increases, potentially to unsafe levels.


Verification / Alternative check:

Compare with an open: replacing an element by an open makes RT → ∞ and I → 0, which truly prevents current. Therefore, “prevents current” describes an open, not a short, in a series path.


Why Other Options Are Wrong:

  • “True” confuses short with open.
  • Polarity reversal does not convert a short to an open; current direction changes sign but still flows.
  • “Only when the short is across the source terminals” actually creates extremely large current, still not zero (though it is a dangerous fault).
  • AC/reactive specifics do not change the fundamental effect of a short’s very low impedance.


Common Pitfalls:

Assuming “fault” automatically means no current. Shorts can cause excessive current and damage rather than interruption.


Final Answer:

False

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