Give two factors that will increase the magnetic field strength of an electromagnet

1). Increase the number of turns of wire in the coil around the magnetm 2). Increase the current through the wire in the coil.

Magnetic field caused by a current carrying conductor - electromagent - wrapped around a soft iron core. It has N uniformly wound turns over a length of L and carries a current of i amperes.

n = N / L = number of turns per unit length

Magnetic field strength = B = Mu n i Mu magnetic permeability

To increase B, We may increase number of turns / unit length OR we can increase the current through the coil of the electromagnet.