Question

What is needed to produce an electromagnet?

Answer 1

• A source of DC electric current eg a battery, with a switch.
• A long length of conducting wire wound into turns.
• A susceptible metal to use as a core to wind the conductor around.

Then while current flows, the metal core will be an electromagnet with magnetic poles, the polarity that may be obtained via the right hand rule.
The stronger the voltage source and the higher the relative permeability of the core and the more the windings, the shorter the length of the core, the stronger will be the magnetic flux density inside the core given in magnitude by
`B=muH=(mu_0mu_rNI)/L`.