The fuse blows off by

Question

Examoogle · Accepted Answer

melting

Explanation: A fuse is a safety device designed to break a circuit when excessive current flows through it. The working principle relies on the thermal effect of electric current, where the conductive material reaches its melting point and breaks the continuity of the circuit.

Working Principle: When current exceeds the fuse's rated capacity, the heat generated, governed by $H = I^2Rt$, causes the fuse element to reach its melting point. Once melted, the physical link is severed, creating an open circuit that prevents further flow of current, thus protecting the downstream components.

Key Formulas: $H = I^2Rt$ — Joule's law of heating determining the heat energy generated in the fuse element.; $I_{fuse} = k \cdot d^{1.5}$ — Preece's law relating fuse current to wire diameter $d$.

Key Points: Fuses operate on the thermal effect of electric current.; The material used for fuses (e.g., Lead, Tin, Copper) has a low melting point.; The fuse provides protection against short circuits and overloads.; Once the fuse blows due to melting, it must be replaced as it is a single-use device.

Advantages: Simple and inexpensive construction; Provides reliable current interruption during faults

Disadvantages: Requires manual replacement after operation; Aging of the fuse element can lead to nuisance blowing

Applications: Domestic wiring circuits; Power distribution transformers; Electronic device circuit boards

Additional Info: Arcing is a phenomenon that occurs during the breaking of a circuit, but the initial trigger for the fuse blowing is the melting of the element.. Burning is an oxidation process, whereas melting is a physical phase change caused by heat.

Answer: C is correct — The fuse element breaks the circuit due to the melting of the conductive material caused by excessive heat generation.

Exam Tip: Remember that circuit breakers use electromagnetic or bimetallic strips to 'trip', whereas fuses strictly use the melting of an alloy to 'blow'.

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