What are the 3 critical components of an electromagnet and what purpose do they each serve?

A source of electricity, a wire coil, and an iron core  

Explanation:

An electromagnet has three critical components:

1. A source of electricity

This is often a battery.

It generates the electric current that produces the magnetic field.  

2. A wire coil

The wire carries the electric current.

Stacking the wire into loops makes a stronger magnetic field.

The more loops in the coil, the stronger the field.

3. An iron core

An iron core greatly increases the strength of the magnetic field within it and at its ends.

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