An iron rod of 0.2 cm2 cross-sectional area is subjected to a magnetizing field of 1200 Am−1. The susceptibility of iron is 599. The magnetic flux produced is:
μ=4π×10−7(1+599)
=7.536×10−4H/m
The magnetic field produced is
B=μH
=7.536×10−4H/m×1200Am−1
Magnetic flux, ϕ=→B.→A=BAcosθ
Assuming field is applied perpendicular to the cross sectional area (→B|−→|A)
ϕ=BA=7.536×10−4H/m×
1200Am−1×0.2×10−4m2
=1.81×10−5Wb
Hence, option (b) is correct.