Question

provide at least 3 variables that can affect the strength of an electromagnet

Answer 1

One equation for the magnetic field generated by an electromagnet is as follows:\[B=\frac{ NI \mu }{ L }\]Where B is the magnetic field; N is the number of turns of wire around the core of the electromagnet; I is the electric current through the wire; μ is the magnetic permeability of the material from which the core of the electromagnet is made; and L is the length of the core of the magnet.

There are some pretty strong hints in that equation.