Question

A student connects a battery to a wire and wraps the wire around an iron nail to produce an electromagnet. Which action should the student take to increase the number of paper clips the electromagnet can pick up? a. He should reduce the number of turns. b. He should replace the iron nail with a plastic spoon. c. He should add another battery. d. He should decrease the current through the wire.

Answer 1

c. He should add another battery.

Adding a battery increases the voltage and (assuming the wire and battery can handle it) increases the current through the coil, which strengthens the magnetic field and lets the electromagnet pick up more paper clips. Reducing turns, using a nonmagnetic core (plastic), or decreasing current would all weaken the magnet.