Читать книгу Essentials of MRI Safety - Donald W. McRobbie - Страница 60

The field generated at the centre of a solenoid of length d with windings of density N turns per metre ‐ this now looks more like a MR superconducting magnet‐ is

(2.1)

θ is the angle measured from the vertical at iso‐centre to the end of the solenoid (Figure 2.7). For very long solenoids θ tends to 90° (π/2) and the field is

(2.2)

Figure 2.7 Solenoid coil showing the angle θ. For a very long solenoid θ →90°.

This is where the definition of magnetic field strength or intensity H in A m⁻¹ (from Chapter 1) comes in, as

(2.3)