Retentivity insight: Materials with low retentivity (low residual magnetization) do not retain magnetic fields well after the magnetizing force is removed. True or false?

Introduction / Context:
Retentivity (residual flux density) describes how much magnetization remains in a material when the external magnetizing field is reduced to zero. It is a key property in selecting materials for permanent magnets versus transformer cores.

Given Data / Assumptions:

• Retentivity is read from the hysteresis loop as the intercept of B when H returns to zero.
• Coercivity measures the reverse H needed to demagnetize the material.
• “Low retentivity” means small residual B after magnetizing field removal.

Concept / Approach:

Materials with low retentivity quickly lose their magnetization once the applied field is removed, making them unsuitable for permanent magnets but suitable for transformer/inductor cores where low residual magnetization and low loss are desired.

Step-by-Step Solution:

Verification / Alternative check:

Compare hysteresis loops: soft magnetic materials (e.g., silicon steel) show low retentivity and coercivity; hard magnetic materials (e.g., Alnico, NdFeB) show high retentivity and coercivity. Observations align with the statement.

Why Other Options Are Wrong:

• “False” would suggest low-retentivity materials keep strong magnetization, which contradicts experimental hysteresis behavior and standard materials data.

Common Pitfalls:

Confusing retentivity with permeability or coercivity; while related, each parameter reflects a different aspect of magnetic behavior and must be evaluated separately for applications.

Final Answer:

True