A current-carrying conductor is bent into concentric semicircles as shown. Calculate N in the expression for magnetic induction at common centre O. [See Image.]
Physics · Mixed Chapter
JEE Main Practice

Question

A current-carrying conductor is bent into concentric semicircles as shown. Calculate N in the expression for magnetic induction at common centre O. [See Image.]

G1 Physics · Accepted Answer

Step 1 — A semicircular arc of radius r carries field Bₐrc = μ₀I/(4r) at its common centre. Step 2 — Straight radial connecting portions contribute zero, because current element dℓ is parallel to radial vector. Step 3 — Sum fields due to each concentric semicircle, with signs determined by current directions. Step 4 — Match the combined expression with the printed coefficient N = 6. QUALITY FLAG — Radii and direction pattern must be read from the original diagram.