Have you not heard of skin effect? The tendency of alternating current is to concentrate more on the 'skin' or the circumference of the conductor rather than on the core. Hence, irrespective of the cross section, a major portion of the current will be in the exteriors of the conductor. As forces are acting outsied the conductor (either attractive or repulsive) the circumferential current is significant rather than the core current.
DC Current? No skin effect but the force remains the same.
OP: The force ahs nothing to do with the conductor - it is the interaction of the magnets - the flowing current creates a magnetic field and that field interacts with the other conductor's magnetic field/ external magnetic Field and that creates the force.
If you want the stress on teh conductor then of course the crossection and would come in but that is another subject (more on the mechanical side)
About Force Calculation
Re: About Force calculation
