For example, i saw a simple electric generator constructed with magnets and fine wire which was spooled to react against the magnets. Is there an advantage to having a spool of fine wire rather than a solid block of copper?
A generator works by using moving magnets to create a changing magnetic field through a loop of wire. When a magnetic field changes through a loop of wire a current arises in the wire to produce an opposing magnetic field. That current is what we want to generate. If you had one solid piece of copper you would be generating the current from one loop. By having multiple wires you can multiply that current by the number of loops you have (say 50,000). More loops more current.
The copper you saw actually has an insulator sprayed onto the outside, so it doesn't touch the other winds in the coil. So yes, the reason is that the inductance increases the more turns you have of a coil, or in the case of a motor, the electromagnetic force increases with more turns.
because its easy to make a cord out of many small wires,instead of one big wire
