Читать книгу Essentials of MRI Safety - Donald W. McRobbie - Страница 82

If the object is non‐spherical and has an axis at an angle θ with respect to B, there will be a twisting force or torque acting to align the object with the field. Torque, T, is a vector (Figure 2.21) with a magnitude

(2.14)

Figure 2.21 Torque Τ on a ferromagnetic object of length l. The force on either end is F = Τ/(0.5l) assuming a central axis of rotation.

Torque is measured in newton‐metres (N m). m is the object’s magnetic moment (= MV).