What is the difference between ferromagnetic, paramagnetic, and diamagnetic materials?
• Ferromagnetic (Fe, Ni, Co): μᵣ up to thousands; strongly magnetized and retains magnetism.
• Paramagnetic (Al, Pt): μᵣ slightly > 1; weakly magnetized, no retention.
• Diamagnetic (Cu, water): μᵣ slightly < 1; weakly repelled by magnetic fields.
 

What is magnetic hysteresis?

Hysteresis is the phenomenon where the B-H curve follows different paths during magnetization and demagnetization. Energy dissipated per cycle equals the area of the hysteresis loop. Hard magnetic materials have large loops; soft magnetic materials have small loops.

What are Coercivity (Hc) and Remanence (Br)?
• Remanence (Br): residual flux density after the external field is removed.
• Coercivity (Hc): the reverse field needed to reduce magnetization to zero. Permanent magnets require high Br and high Hc; transformer cores need low Hc to minimize losses.
 

What is magnetic saturation?

Saturation occurs when all magnetic dipoles are aligned, so B no longer increases proportionally with H. The B-H curve flattens beyond this point. Core designs must avoid saturation to maintain linear behavior.

What is core loss (iron loss)?

Core loss has two components：
•Hysteresis loss = frequency × B-H loop area (domain switching energy).
•Eddy current loss = I²R heating from induced currents in the core. Using laminated cores greatly reduces eddy current loss.