Question

Explain why you have to close the switch in order for the electromagnet to pick up any paperclips.

Answer 1

Answer:

That's because a coiled wire creates a stronger magnetic field than a simple length of wire (the more coils, the stronger the field), and adding an iron nail in the middle boosts that field even more. The wire itself did not pick up the paper clip (its magnetic field was too weak), but the nail and coiled wire did.