Question

A group of students were investigating the strength of electromagnets and wanted to find out if increasing the number of coils or increasing the size of the iron core made the electromagnet stronger. To test the strength of the different variations, the students counted how many paperclips the electromagnet could pick up. The students first increased the number of coils while using the same size core. The students then increased the core while using the same number of coils.



Results:



Increasing the Strength of an Electromagnet



Number of Paper Clips

Number of Paper Clips

Which is Strongest?

Number of Coils

30 Coils

60 Coils

✔

9

23

Size of Iron Core

Small Iron Core

Large Iron Core



26

5



Which statement explains why increasing the number of coils made the electromagnet stronger than increasing the size of the iron core?



A.
Increasing the number of coils provides a greater distance along the wire for the current to travel.

B.
Increasing the number of coils increases the amount of magnetic force generated by the electromagnet.

C.
Increasing the size of the iron core causes the electrons to travel farther which decreases the magnetic field generated by the electromagnet.

D.
Increasing the size of the iron core increases the number of turns in the coil, decreasing the magnetic field strength generated by the electromagnet.

Answer 1

B.

Adding more coils increases the electromagnet's ampere‑turns (N·I), so the magnetic field strength grows as the number of turns increases. Increasing the core size does not increase the ampere‑turns and may not improve (and can even reduce) the effective magnetization.