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Q18 (NDA-II/2018) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism Answer Verified

The magnetic field strength of a current carrying wire at a particular distance from the axis of the wire

Result
Your answer: —  Â·  Correct: A
Explanation

The magnetic field strength (B) produced by a current-carrying wire at a specific distance (r) from its axis is directly proportional to the magnitude of the electric current (I) flowing through it. According to the Biot-Savart law and Ampere's circuital law, the mathematical expression for the magnetic field outside a long straight conductor is B = (μ₀I) / (2πr). This formula demonstrates that the field strength depends explicitly on the current and the radial distance from the wire. While the field pattern depends on the shape of the conductor [1], for a fixed distance from the axis of a straight wire, the current is the primary determining factor for field magnitude. The radius of the wire only affects the field calculation for points inside the conductor, and temperature is not a variable in the standard magnetic field equations for conductors.

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 12: Magnetic Effects of Electric Current > What you have learnt > p. 206
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