A mechanic dropped a bolt he needed to repair a car motor. He decided to make a simple electromagnet to try to attract the metal bolt. Which list of materials would make the best electromagnet?
a
metal rod for a core, copper wire, 9-volt battery
b
wooden rod for a core, copper wire, 9-volt battery
c
plastic rod for a core, copper wire, 9-volt battery
d
glass rod for a core, copper wire, 9-volt battery
a
metal rod for a core, copper wire, 9-volt battery