The magnetic moment of an iron bar is \(\mathrm{M}\). It is now bent in such a way that it forms an arc section of a cir…

• Arc Length = L = Rθ (θ=π/3). Chord Length L' = 2Rsin(θ/2) = 2Rsin(π/6) = R. Since R = L/θ = 3L/π, the new magnetic length is L' = 3L/π.
• New Moment M' = m × L' = m × (3L/π). Substitute m = M/L. M' = (M/L) × (3L/π) = 3M/π.

(NEW NCERT 12^th Page No. 137, 138)