A fuse is connected

Question

A fuse is connected

Examoogle · Accepted Answer

in series with circuit

Explanation: A fuse is a safety protection device that must be connected in series with the phase wire of the electrical circuit. By being in series, the entire load current flows through the fuse element, allowing it to detect and interrupt the circuit immediately when the current exceeds a predetermined threshold.

Working Principle: The fuse operates on the heating effect of electric current ($H = I^2Rt$). When a fault condition such as a short circuit or overload occurs, the current significantly increases, causing the fuse element to melt due to excess heat. Because it is connected in series, the melting of the element creates an open circuit, effectively isolating the load from the power supply and preventing damage.

Key Formulas: $H = I^2Rt$ — The principle of Joule heating which causes the fuse element to melt; $I_{fuse} \approx 1.25 	imes I_{rated}$ — Typical rating guideline for fuse selection

Key Points: Always connected to the 'Live' or 'Phase' wire, never the 'Neutral'.; Acts as an overcurrent protection device to prevent fire hazards and equipment damage.; The fuse link consists of a low-melting-point material like lead, tin, or copper alloys.

Advantages: Simple and inexpensive design; Provides reliable current-limiting protection; Acts instantaneously under high-fault current conditions

Disadvantages: Non-reusable (must be replaced after operation); Can lead to single-phasing in 3-phase systems if only one fuse blows; Potential for nuisance tripping due to aging

Applications: Domestic wiring systems; Power distribution transformers; Industrial control panels

Additional Info: A fuse connected in parallel would result in a direct short-circuit path when the fuse blows, bypassing the load.. Fuses are classified into Rewirable and HRC (High Rupturing Capacity) types.

Answer: A is correct — A fuse is connected in series with the circuit to ensure all load current passes through it, enabling it to break the circuit during overcurrent events.

Exam Tip: In competitive exams, remember that protection devices like Fuses and MCBs (Miniature Circuit Breakers) are always in series, while voltage monitoring devices like Voltmeters are always in parallel.

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