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The magnetic induction at a point P which is at a distance of 4 cm from a long current carrying wire is 10⁻³ T. The field of induction at a distance 12 cm from the current will be
- 3.33 × 10⁻⁴ T
- 1.11 × 10⁻⁴ T
- 3 × 10⁻³ T
- 9 × 10⁻³ T
Correct answer: 1.11 × 10⁻⁴ T
Solution
The magnetic field due to a long current-carrying wire is inversely proportional to the distance from the wire (B ∝ 1/r). Given B₁ = 10⁻³ T at r₁ = 4 cm, we calculate B₂ at r₂ = 12 cm using B₂ = B₁ × (r₁/r₂). Substituting values, B₂ = 10⁻³ × (4/12) = 1.11 × 10⁻⁴ T.
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