Full text loading...
The transient electric field excited by a step current in a loop of radius a on the surface of a ground of conductivity σ and permeability μ0 are concentrated in a toroidal zone. At early times the zone moves slightly inward from the loop and down but at later time the field maximum moves along a cone dipping at 30° away from the loop. At later times the maximum occurs beneath a point on the surface at radius R where R2 ≈ 2.56 t/σμ0. At this maximum the time rate of change of the radial magnetic induction is zero.