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Question: A magnetising field of 1500 A mT-1 produces flux of 2.4 ×10-5 weber in a iron bar of the cross-secti...

A magnetising field of 1500 A mT-1 produces flux of 2.4 ×10-5 weber in a iron bar of the cross-sectional area of 0.5 cm2. The permeability of the iron bar is

A

245

B

250

C

252

D

255

Answer

255

Explanation

Solution

: Here, H=1500Am−1,ϕ=2.4×10−5\mathrm { H } = 1500 \mathrm { Am } ^ { - 1 } , \phi = 2.4 \times 10 ^ { - 5 } weber

A=0.5 cm2=0.5×10−4 m2\mathrm { A } = 0.5 \mathrm {~cm} ^ { 2 } = 0.5 \times 10 ^ { - 4 } \mathrm {~m} ^ { 2 }

∴B=ϕA=2.4×10−50.5×10−4=4.8×10−1 T\therefore \mathrm { B } = \frac { \phi } { \mathrm { A } } = \frac { 2.4 \times 10 ^ { - 5 } } { 0.5 \times 10 ^ { - 4 } } = 4.8 \times 10 ^ { - 1 } \mathrm {~T}

And μ=BH=4.8×10−11500=3.2×10−4\mu = \frac { B } { H } = \frac { 4.8 \times 10 ^ { - 1 } } { 1500 } = 3.2 \times 10 ^ { - 4 }

So relative permeability