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The material used for fuse must have
low melting point and high specific resistance
low melting point and low specific resistance
high melting point and low specific resistance
low melting point and any specific resistance
low melting point and high specific resistance
A fuse is a protective device designed to interrupt an electrical circuit when current exceeds a predetermined limit. To perform this function effectively, it must melt quickly under overload conditions, necessitating a low melting point, and ensure heat generation at the rated current is manageable, requiring appropriate resistive properties.
A fuse is a protective device designed to interrupt an electrical circuit when current exceeds a predetermined limit. To perform this function effectively, it must melt quickly under overload conditions, necessitating a low melting point, and ensure heat generation at the rated current is manageable, requiring appropriate resistive properties.
H=I2Rt тАФ Joule's Law of heating
R=╧БALтАЛ тАФ Resistance formula where ╧Б is specific resistance
The principle of operation is based on the heating effect of electric current, defined by Joule's Law H=I2Rt. A high specific resistance ensures that even with a short length, the fuse wire generates sufficient heat (I2R) to reach its melting point rapidly during a fault. A low melting point ensures that the wire breaks or 'blows' quickly, thereby isolating the faulted circuit segment from the supply.
The fuse wire must act as a weak point in the circuit to protect expensive components.
Common materials used for fuses include lead, tin, zinc, or alloys of these metals.
Copper is generally avoided for low-current fuses due to its high melting point, though it is used in high-voltage HRC fuses.
Simple and inexpensive protection mechanism.
Highly reliable as it does not rely on complex mechanical parts or sensors.
Requires manual replacement after operation.
Cannot be used for multiple operations unlike a Circuit Breaker (MCB).
Domestic wiring protection.
Industrial control panels.
Automotive electrical systems.
High specific resistance allows the fuse to be compact while maintaining the required resistance.
Option B is incorrect because low specific resistance would require a very long or very thin wire to generate heat, which is physically impractical.
Option C is incorrect because a high melting point would prevent the fuse from melting during an overload, defeating the purpose of protection.
A is correct тАФ The fuse material must possess a low melting point to ensure rapid breaking and a high specific resistance to generate sufficient heat during overload conditions.
Always remember that fuses protect against overcurrent, while relays and MCBs are preferred for applications requiring repetitive switching or adjustable settings.