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Q4 (CDS-II/2021) Science & Technology ā€ŗ Basic Science (Physics, Chemistry, Biology) ā€ŗ Electricity and magnetism Answer Verified

An electric circuit is consisting of a cell, an ammeter and a nichrome wire of length l. If the length of the wire is reduced to half (l/2), then the ammeter reading

Result
Your answer: ā€”  Ā·  Correct: B
Explanation

The resistance (R) of a conductor is directly proportional to its length (l) and inversely proportional to its cross-sectional area (A), expressed as R = Ļl/A [1]. In an electric circuit with a constant voltage source (cell), Ohm's law states that the current (I) is inversely proportional to the resistance (I = V/R). When the length of the nichrome wire is reduced to half (l/2), its resistance also decreases to one-half of its original value. Since the resistance is halved, the current flowing through the circuitā€”and consequently the ammeter readingā€”gets doubled. This relationship is a fundamental principle of electricity where reducing the path length for electrons decreases the number of collisions with lattice ions, thereby lowering resistance and increasing current flow.

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > Activity 11.3 > p. 178
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