Question

How could the strength of an electromagnet be increased?

by reducing the length of the core (nail) of the electromagnet

by using the rubber material as the core for the electromagnet

by decreasing the amount batteries used for the electromagnet

by increasing the number of coils in the wires of the electromagnet.

Answer 1

increasing coil wires is correct, like the other person answered.

Answer 2

I had this question on a test in K12

The answer is By increasing the number of coils in the wires of the electromagnet.