Question

Andreas has to make an electromagnet in his science class. He was only given a nail, copper wire, and a 9-volt battery. The assignment was to make a magnet strong enough to pick up paper clips. His teacher decided to make the assignment into a competition to see whose magnet could pick up the most clips.

What can Andreas do to his magnet to make sure he wins by picking up the most paper clips?

A.
Andreas can wrap few coils of the wire, close together, around the nail.

B.
Andreas can wrap few coils of the wire, far apart, around the nail.

C.
Andreas can wrap many coils of the wire, far apart, around the nail.

D.
Andreas can wrap many coils of the wire, close together, around the nail.

Answer 1

D. Andreas should wrap many coils of the wire close together around the nail.

Reason: the magnetic field of a solenoid is proportional to the number of turns per unit length (n) times the current (I). More tight, closely spaced turns increase n and concentrate the field through the nail, producing a stronger electromagnet capable of picking up more paper clips.