JAMB - Physics (1980 - No. 31)
The best material for the core of the primary and secondary coils of an induction coil is
copper, because it has a good conductor of electricity
steel, because it becomes magnetic and retains its magnetism for a long time
rubber, because it is a good insulator and the user is prevented from shock
soft iron, because it becomes magnetic but easily loses its magnetism
glass, because it is transparent