From Ampere's circuital law for a long straight wire of circular cross-section carrying a steady current, the variation of magnetic field in the inside and outside region of the wire is (a) Uniform and remains constant for both the regions. (b) A linearly increasing function of distance upto the boundary of the wire and then linearly decreasing for the outside region. (c) A linearly increasing function of distance r upto the boundary of the wire and then decreasing one with 1/r dependence for the outside region. (d) A linearly decreasing function of distance upto the boundary of the wire and then a linearly increasing one of the outside region.

Answer: (c). Inside: B = (μ₀ I r)/(2π R²), linear in r. Outside: B = (μ₀ I)/(2π r), falls as 1/r. So the answer is (c).

From Ampere's circuital law for a long straight wire of circular… | NEET 2022 (Phase 1)

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Ampere's Law, Cylinders, Solenoid & Toroid

From Ampere's circuital law for a long straight wire of circular cross-section carrying a steady current, the variation of magnetic field in the inside and outside region of the wire is

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Answer: (c)

Inside: $B = \frac{\mu_0 I r}{2\pi R^2}$ , linear in $r$ .
Outside: $B = \frac{\mu_0 I}{2\pi r}$ , falls as $\frac{1}{r}$ .
So the answer is (c).

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