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

The Correct Option is B

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.