The moment of a short magnet is 4 amp-m2. The magnetic induction at a point on the axial line at a point 40 cm away from its mid-point is
0⋅125×10−4 web /m2
0⋅150×10−4 web /m2
0⋅175×10−4 web /m2
2.0×10−4 web /m2
B=μ04π×2Md3B=10−7×(2×4)40×10−23=0⋅125×10−4 web /m2