We have probably all seen the demonstration of magnetic braking where a magnet swings by a piece of solid copper and the induced current slows the travel of the magnet.
Presumably a shorted coil of wire will have the same effect.
The question is, for a given mass of copper which is more effective - coil or slab?
If you want the braking effect over a larger distance, the coil needs have a larger area but, the problem that arises is that the flux from the moving magnet is concentrated in a fraction of the static coil's aperture area and, braking would tend to be less effective. Scale this problem up and you might see what I mean.
It boils down to the induced voltage in the static coil and, how much current will circulate due to that coil being shorted and, in return, how much "counter-magnetism" is produced by that coil current in the vicinity of the magnet.
With a larger diameter, the coil's counter magnetism is produced over the whole of its larger aperture and therefore, the flux density is diminished in all areas. The total flux would probably be the same but, it's a bigger area hence, the flux density (the thing that is trying to "fight" the magnet) is smaller in the magnet's vicinity.
This is of less consequence for the solid conducting sheet (even if the resistance does grow somewhat due to it thinning out).
The question is, for a given mass of copper which is more effective - coil or slab?
My money is on the slab of copper. But, if coil area and magnet are about the same size, then there won't be much difference.
The solution depends on cost but the lower the impedance, the higher the current and force.
Lenz's Law is basically changing a magnetic field (moving a magnet) next to a non-magnetic metal will induce an electric field (a voltage difference) in the metal, which subsequently generates a magnetic field with an opposite orientation with respect to your magnet.
With Litz wire using almost as much copper as solid, one can reduce the inductance by parallel insulated strands or loops. Yet L is constant for any square or cube or similar blob regardless of size and it is very small meaning the cutoff frequency is so high ( imagine power/ground plane inductance in PCB BW in GHz) There may be no advantage to using Litz coils unless it is a cost reduction to solid copper.. For example in HDDs, the rotary voice coil motor is surrounded by solid copper, yet it is only thin foil. This reduces the MMF sufficiently.
Solid.
A stranded construction (such as a shorted coil with turns N >> 1) prevents current flow at sideways directions to the wire; the wires are insulated from each other.
This prevents currents in those directions from flowing, and thus opposing motion in those directions, or due to the fringing fields around said magnet.
This will vary with arrangement, as, for example, the windings in the stator of a motor will hardly be able to experience sideways field motion at all when the magnet (assuming a magnetized rotor) can only spin. But for the only example given (if merely by way of introduction), the fields will be quite nonuniform, and the lone magnet in free space might tumble and such, and so all these other directions can very much come into play.
A note about copper mass: remember that, for wire turns, there must also be insulation separating it, and some wasted space (even square wire isn't perfectly square, but has rounded corners). So for the same effect, the magnet needs to be larger, but by how much is not obvious. For example, with respect to the tumbling of a free magnet, a relative larger torque might be applied (torque moment goes as length squared), assuming wire has been wound in such a direction to capture that motion.
