Читать книгу Essentials of MRI Safety - Donald W. McRobbie - Страница 75

What is the maximum force on an iron rod of length 10 cm, diameter 2 cm in the fringe field of a MRI magnet with B = 100 mT and dB/dz = 0.6 T m⁻¹? The material is unsaturated.

The material is unsaturated (see Example 2.2), so use Equation 2.12

By contrast the gravitational force is

The magnetic force is approximately eight times the force due to gravity at this point.

Figure 2.18 Influence of angulation of ferromagnetic objects with respect to the B₀ direction. The objects have density of 8000 kg m⁻³ weighing 0.1 kg with χ = 1000 and B_sat = 1.6 T. B = 0.1 T and dB/dz = 0.5 T m⁻¹. The effect of saturation at around 30° is evident for the longest object. Simulation for illustration only.