Question

A magnetizing field of 1000 A/m produces a magnetic flux of 2.4 x 10-5 Wb in an iron bar of cross-sectional area 0.3 cm2.The magnetic permeability of the iron bar in SI unit is

• A. 2.5 x10–4
• B. 8 x 10–4
• C. 5 x 10–4
• D. 4 x 10–4

Answer 1

Answer: (B)

8 x 10–4

Answer 2

The magnetic flux (Φ) through a material is:
Φ = B * A
Given:
Magnetizing field (B) = 1000 A/m
Magnetic flux (Φ) = 2.4 x 10-5 Wb
Cross-sectional area (A) = 0.3 cm²
First, we need to convert the cross-sectional area from cm² to m²:
A = 0.3 cm² = 0.3 x 10-4 m²
Rearranging the equation
Φ = B * A,
we can solve for B:
B = $\frac {Φ}{A}$
Substituting the given values:
B = $\frac {2.4 \times 10^-5 \ Wb}{0.3 \times 10^-4 \ m² }$
B = $\frac {2.4 \times 10^-5 \ Wb}{3 \times 10^-5 \ m² }$
B = 0.8 Wb/m²
μ = $\frac {B}{H}$
μ = $\frac {0.8 \ Wb/m² }{1000 \ A/m}$
μ = 8 x 10-4 (Wb/A)
The magnetic permeability in SI units is henries per meter (H/m). Since 1 Wb/A = 1 H, we have:
μ = 8 x 10-4 H/m
Therefore, the correct answer is (B) 8 x 10-4.