Question

What are two ways you can increase the magnetic field of an electromagnetic?

Answer 1

1).  Wind more turns of wire in the coil around the core.

2).  Increase the electrical current flowing in the wire.
(You can do that by using a battery or power supply with a little more voltage.)

3).  If the core of the electromagnet is anything else but pure iron,
take it out, throw it away, and replace it with a core of pure iron.