CBSE 2026 · Region 1 · Set 1 · Q3 · 1 mark
A long straight wire of circular cross-section (radius a) carries a steady current I. The current is uniformly distributed across this cross-section. The magnitude of the magnetic field produced at a point at a distance (a/$\displaystyle 2$) from the axis of the wire will be
Official answer
From CBSE’s own marking scheme for this paper.
(C)
$\displaystyle \frac{\mu_{0} \mathrm{I}}{4 \pi \mathrm{a}}$
Moving Charges and MagnetismAmpere’s Circuital LawApplymcqmedium
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CBSE Class 12 Physics past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.