Air core Coils vs. Metal core coils

[Jdo300]

Hi, I have a quick question. I was just wondering which type of coil is best for inducing electricity. If I pass a magnet over one end of the coil, would a metal core help more current to be induced or would an air coil be better?

Thanks,
Jason O

 

[Cliff_J]

Since the metal core helps increase the flux density, and the magnetic fields will decrease in strength exponentially with distance, the metal core seems the logical choice. A metal core is used in transformers where the entire purpose is to properly induce a current in the secondary coil based on the magnetic field induced in the core.