22. a) The formation of a hysteresis loop in ferromagnetic substances describes the relationship between the magnetic field strength ($H$) and the magnetic induction ($B$) or magnetization ($M$) of the material. When an external magnetic field is applied to an unmagnetized ferromagnetic material, its magnetic domains align with the field, causing the magnetization to increase. As the field increases, the material reaches saturation where all domains are aligned. When the external field is then reduced to zero, the magnetization does not return to zero but retains some residual magnetism, known as remanence. To reduce the magnetization to zero, a reverse magnetic field must be applied, which is called the coercive field. As the reverse field increases, the material becomes magnetized in the opposite direction, eventually reaching saturation in the reverse direction. Reducing this reverse field to zero again leaves a reverse remanence, and applying a forward field completes the loop. This lagging of magnetization behind the applied field is called magnetic hysteresis. b) • Soft iron exhibits a narrow hysteresis loop. This signifies that it has low retentivity and low coercivity. Soft iron is easily magnetized and demagnetized, making it suitable for electromagnets and transformer cores where frequent changes in magnetization are required. • Steel exhibits a wide hysteresis loop. This signifies that it has high retentivity and high coercivity. Steel is difficult to magnetize and demagnetize, meaning it retains its magnetism strongly once magnetized. This property makes steel suitable for permanent magnets. c) The hysteresis loop illustrates the magnetic properties of a material.