I got a coil and a rod magnet is moved back and forth. In order to obtain the greatest current, should the rod be as long as possible? What factors affect the ac current that will be generated? no of coil per length, strength of magnet and? What formula should I use?
And how can I keep the output voltage and out current steadily?

 

The formula: B*L*v, where "B"= the magnet strength, "L"=the coil inductivity,"v" = the speed (of moving)
When the speed is constant, the output also.