Question

4.2.4 quiz: electromagnetism
question 6 of 10
which combination of a wire coil and a core would make the strongest electromagnet?
a. 90 coils of insulated wire around a steel bolt
b. 50 coils of bare wire around a steel bolt
c. 90 coils of bare wire around a hollow cardboard core
d. 50 coils of insulated wire around a hollow cardboard core

Explanation:

To make a strong electromagnet, we need a ferromagnetic core (like steel) as it can be easily magnetized. Also, more coils of wire (90 coils instead of 50) will increase the magnetic field. Insulated wire is better than bare wire around the core. Insulated wire allows more coils to be closely packed without short - circuiting between adjacent turns.

Answer:

A. 90 coils of insulated wire around a steel bolt