A magnetizing field of 500 A/m produces a magnetic flux of 4×10-5 Wb in an iron rod of cross-sectional area 0.4cm2 . The permeability of the rod in W/b/A-m is

MHT CET · Physics · Magnetic Properties of Matter

A magnetizing field of 500 A/m produces a magnetic flux of $4 \times 10^{- 5}$ Wb in an iron rod of cross-sectional area $0.4 c m^{2}$ . The permeability of the rod in W/b/A-m is

A $4 \times 10^{- 6}$
B $1 \times 10^{- 3}$
C $2 \times 10^{- 4}$
D $3 \times 10^{- 5}$

Verified Solution

Answer & Solution

Correct Answer

(C) $2 \times 10^{- 4}$

Step-by-step Solution

Detailed explanation

Given, magnetising field, H = 5000 A/m
Magnetic flux,

ϕ = 4 \times 10^{- 5} W b

Cross-sectional area, A = 0.4

c m^{2} = 4 \times 10^{- 5} m^{2}

∴

Permeability of rod,

μ = \frac{B}{H} = \frac{ϕ}{A H} [∴ ϕ = B A \Rightarrow B = \frac{ϕ}{A}]

= \frac{4 \times 10^{- 5}}{4 \times 10^{- 5} \times 5000} = 2 \times \frac{10^{- 4} W b}{A} - m

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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