Practice question

**Permanent magnet requirement** is high retentivity to maintain field and high coercivity to resist demagnetization. Ability to retain magnetism after field removal is property of hard ferromagnets, related to domain wall pinning and anisotropy. An iron nail, being a ferromagnetic material, becomes magnetized in the non-uniform field of a bar magnet, developing an induced magnetic moment. The field's gradient causes a net force toward the stronger region (typically the pole), while the misalignment of the induced moment with the field produces a torque. Substituting values gives The non-uniform field inducing a magnetic moment, which matches expected magnitude for this magnetic configuration, confirming dipole field dependence