First an emf is just the line integral of the electric field
around some closed path. E-fields produced by static charges cannot
generated emfs. Only nonconservative E-fields (those produced by changing
magnetic fluxes) can produce emfs. The emf produced on any closed path is
proportional to the rate of change of the magnetic flux through that
particular path. Thus, paths with little cross-sectional area produce
very small emfs at best. So there will be no eddy currents in the wire if
it is a thin wire. On the other hand, the whole wire loop has a large
cross-sectional area so a fairly large emf is generated (whether or not
the loop is closed). With the loop open no current flows, with it closed
current flows. In the first case it is easy to push the magnet towards
the loop, in the second it is hard to push it towards the loop.
Mark
Dr. Mark H. Shapiro
Physics Department
California State University, Fullerton
P.O. Box 6866
Fullerton, California 92834-6866