Question

an electromagnet is created using a battery , an insulated copper wire and and an iron nail . the wire is wrapped around the nail 20 times and attached to the battery. which pair of changes will definitely increase the strength of the electromagnet

Answer 1

C) Increase the voltage of the battery and increase the number of turns of the coil.

According to the ideal transformers equation Ns/ Np = Vs/Vp where s= secondary and p= primary, number of turns is proportional to voltage so a increased number of turns and increased voltage result in a higher power.

Hope I helped!