Along the equatorial line, magnetic field strength B=4πμ0(r2+ℓ23/2M) Given: M=4 JT−1 r=200 cm=2 m ℓ=26 cm=3 cm=3×10−2 m ∴B=4π4π×10−7×[22+(3×10−2)2]3/24 Solving we get, B=5×10−8 tesla
JEE Main 2012 — Physics Electromagnetism
A bar magnet of length 6 cm has a magnetic moment of 4 J T−1. Find the strength of magnetic field at a distance of 200 cm from the centre of the magnet along its equatorial line.
Held on 7 May 2012 · Verified 6 Jul 2026.
4×10−8 tesla
3.5×10−8 tesla
5×10−8 tesla
3×10−8 tesla
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