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.

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 ...

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 ...