how does electromagnetism effect the function of a generator (using magnetism to produce electrical energy)

We know that a changing magnetic field induces a current in a conductor. For that reason a generator basically consist an element that produces a magnetic field that changes over time and a conductor where the current will be induced.

This element that produces a magnetic field can be one of the following:

- A permanent magnet: Which is basically like a regular magnet. The magnetic field that a permanent magnet produces does not change over time, we need a motor or any other external force to move the axis of the generator and cause the magnetic field to change.

- An electro-magnet. Which is basically a DC current flowing through a conductor. Basically, when current flows through a conductor it behaves exactly like a magnet. So what we commonly do, is to connect a conductor to a DC battery, and it will create a magnetic field.

Like we are using a DC battery to create a magnetic field, then the magnetic field won't change over time either. So we still need an external force to move the axis of the generator to produce AC electricity.