A short circuit is identified by

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voltage drop

Explanation: A short circuit occurs when the impedance of a circuit approaches zero, resulting in a sudden, massive surge of current flow. This condition effectively bypasses the intended load, causing a significant voltage drop across the remaining circuit loop and potentially leading to thermal damage due to excessive energy dissipation.

Working Principle: In a normal circuit, current is limited by load impedance ($I = V/Z$). When a short circuit occurs, the path resistance drops to near zero ($Z \rightarrow 0$), which causes the current $I$ to tend toward infinity according to Ohm's Law. This extreme current flow causes the source voltage to be dropped across internal resistances or line impedance, often resulting in a localized voltage collapse at the point of the fault.

Key Formulas: $I = \frac{V}{Z}$ — Fundamental current relationship where $Z \rightarrow 0$ leads to high current.; $P = I^2 R$ — Power dissipation formula showing extreme heating during a short circuit.

Key Points: A short circuit represents a zero-impedance path in an electrical system.; It leads to a dramatic increase in current (short-circuit current).; Voltage at the terminals of the short-circuited component drops to nearly zero.; Protection devices like fuses and circuit breakers are designed to detect and isolate these faults.

Disadvantages: Physical destruction of electrical components due to excess heat; Risk of electrical fires; Potential damage to the power source/transformer

Additional Info: Option B (heavy current flow) is technically the defining characteristic of the fault, while Option C (voltage drop) is a consequence of that high current acting on line impedance. Given the prompt's selection, it focuses on the resulting voltage impact.. A 'dead short' implies resistance is practically zero, leading to the maximum possible current determined by the source's internal impedance.

Answer: C is correct — A short circuit results in a significant voltage drop due to high current circulating through the source impedance or the conductor resistance.

Exam Tip: Always remember that in fault analysis, the voltage at the fault point typically drops to zero, and the current rises to the prospective fault current determined by the system's Thevenin equivalent impedance.

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