Behavior of conducting solid or liquid jet moving in magnetic field: (1) paraxial; (2) transverse; (3) oblique

摘要

When a conductor moves through a nonuniform magnetic field, eddy currents flow that interact with the field to decelerate the conductor and perhaps change its trajectory, orientation and, if a liquid, shape. A rod of radius a = 1 cm and the density and electrical conductivity of melted gallium ({gamma} = 6.1 g/cm{sup 3}, {rho} = 26 {micro}{Omega} cm) will decelerate 6.3 m/s in a 0.5 m ramp of paraxial field with a constant gradient g of 40 T/m ({Delta}B = 20 T). The deceleration is proportional to a{sup 2}g{Delta}B/{gamma}{rho}, independent of the velocity. The bar decelerates about twice as much in a 20 T, 0.5 m ramp of transverse field. A bar traveling at a shallow angle to such a field decelerates about 6.3 m/s. If the bar is 0.25 m long and moves at 20 m/s, it aligns with the field in {approximately}10 ms, during which time it advances {approximately}0.2 m.