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Q54 (NDA-I/2013) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism Answer Verified

Metal used to make wires for safety fuses must have

Result
Your answer: —  Â·  Correct: B
Explanation

A safety fuse is a critical protection device designed to break an electrical circuit during overloading or short-circuiting. To function effectively, the fuse wire must possess a low melting point so that it melts immediately when the temperature rises due to excessive current flow [1]. Additionally, the material must have high resistivity (or high resistance) [1]. High resistivity ensures that sufficient heat is generated (based on Joule's law, H = I²Rt) even with a small increase in current, facilitating the rapid melting of the wire. While some sources mention high conductivity for specific industrial applications to reduce ohmic losses [2], the standard pedagogical and safety requirement for domestic fuses—typically made of lead-tin alloys—is high resistivity and a low melting point to ensure timely circuit interruption [1].

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > 11.7.1 Practical Applications of Heating Effect of Electric Current > p. 190
  2. [2] Science , class X (NCERT 2025 ed.) > Chapter 12: Magnetic Effects of Electric Current > What you have learnt > p. 206
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