The current increases. The number of turns in the coil increases. An iron core makes a strong electromagnet which can be easily magnetised and demagnetised.

The field inside a solenoid is strong and uniform ... direction as the current is flowing in the coil. Your thumb points to the north pole of the electromagnet. The magnetic field produced ...

An electromagnetic coil gun takes a line of electromagnets working together to form a moving electromagnetic field. These fields accelerate a project and boom, you have electricity moving matter ...