Читать книгу Essentials of MRI Safety - Donald W. McRobbie - Страница 58

If we have a straight wire and pass a current I along it, then the magnetic field generated will have circular field lines (Figure 2.5). The direction of the field lines can be determined by the “right hand rule”, namely that if your right hand’s thumb represents the direction of current flow, then your cupped fingers will indicate the circular B field direction, denoted B_θ. The magnitude of the field at a radial distance r from the wire is proportional to 1/r. The subscript θ (from polar coordinates‐ see Appendix 2) indicates that the field lines form circular paths around the wire.

Figure 2.5 Magnetic field lines from a long straight conductor carrying current I. The direction of the lines follows the right‐hand rule.