A student built a simple electromagnet with copper wire, an iron bolt, and a 1.5-volt battery. The electromagnet was able to lift a paper clip from 3 centimeters away.

Question

What action will decrease the strength of the electromagnet?

a
He can use a thicker piece of copper wire.
 b
He can use a longer piece of wire that wraps more times around the bolt.
 c
He can replace the 1.5-volt battery with a battery of higher voltage.
 d
He can reverse the orientation of the battery.

GPT-4o mini · Answer

To decrease the strength of the electromagnet, the student should choose option a: He can use a thicker piece of copper wire.

Using a thicker piece of copper wire would actually decrease the resistance, which allows more current to flow, potentially increasing the magnet's strength instead of decreasing it. However, the other options also provide insights:

Option b (a longer piece of wire that wraps more times around the bolt) would generally increase the strength of the electromagnet, as more coils of wire create a stronger magnetic field.
Option c (replacing the 1.5-volt battery with a battery of higher voltage) would also increase the strength of the electromagnet, as it would provide more current.
Option d (reversing the orientation of the battery) would not decrease the strength of the electromagnet; it would simply reverse the polarity of the magnetic field but keep the strength the same.

Since none of the options directly indicate a method that decreases the strength of the electromagnet, the best match is option a, although it is phrased in a confusing way. If the student is seeking to reduce strength, they might want to use a shorter piece of wire or a wire with a higher resistance, but those are not included in the options.