Question

The figure gives experimentally measured B vs. H variation in a ferromagnetic material. The retentivity, co-ercivity and saturation, respectively, of the material are:

• A. 1.5 T, 50 A/m, 1.0 T
• B. 1.0 T, 50 A/m, 1.5 T
• C. 1.5 T, 50 A/m, 1.0 A/m
• D. 1.0 T, 50 A/m, 1.5 A/m

Answer 1

Answer: (B)

1.0 T, 50 A/m, 1.5 T

Answer 2

The B-H curve (hysteresis loop) for a ferromagnetic material illustrates its magnetic properties.

1. Retentivity (or Remanence): This is the magnetic flux density (B) that remains in the material when the magnetizing field (H) is reduced to zero. On the given B-H curve, locate the point where the curve intersects the positive B-axis (i.e., where H = 0). From the graph, this value is 1.0 T.

2. Coercivity (or Coercive Force): This is the magnitude of the reverse magnetizing field (H) required to reduce the residual magnetic flux density (B) to zero. On the graph, locate the point where the curve intersects the negative H-axis (i.e., where B = 0). From the graph, this value is -50 A/m. The coercivity is the magnitude, so it is 50 A/m.

3. Saturation Magnetic Flux Density: This is the maximum magnetic flux density (B) that the material can achieve, even with a further increase in the magnetizing field (H). On the graph, observe the highest B value reached where the curve flattens out at high H. From the graph, this value is 1.5 T.

Therefore, the retentivity, co-ercivity, and saturation are 1.0 T, 50 A/m, and 1.5 T, respectively.