Читать книгу Essentials of MRI Safety - Donald W. McRobbie - Страница 83

For |χ_m| << 1 the torque is [1]:

(2.15)

Perhaps at odds with “common sense” is the observation that the maximum torque is exerted at 45° (Figure 2.22a), but at this angle there is the greatest product of magnetization and interaction with B. The maximum torque for a long object becomes

(2.16)

Figure 2.22 Relative torque as a function of: (a) angle; (b) ratio of length‐diameter for a cylinder for unsaturated ferromagnetic objects.

As χ << 1, the torque on non‐ferromagnetic objects is very small.