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

Answer 1

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 wire would actually decrease the number of turns that can fit on the iron bolt and increase resistance, which leads to less current flowing through the wire. A lower current results in a weaker magnetic field, thereby decreasing the strength of the electromagnet.

The other options would generally increase the strength of the electromagnet:

• b: Using a higher voltage battery would increase the current and thus strengthen the electromagnet.
• c: Reversing the orientation of the battery would not affect the strength of the magnetic field; it would simply reverse its direction.
• d: Using a longer piece of wire that wraps more times around the bolt would increase the strength of the electromagnet, as more turns create a stronger magnetic field.

So the correct option for decreasing the strength of the electromagnet is a.