Are a process uses a length of flux-coated electrode which provides filler material metal and atmospheric shielding?

Are used to grip the electrode. The most common types are the collet and the pincher. The electrode in the collet-type is inserted in the head and grip by twisting the handle.

It is designed to provide either DC or AC outputs.

Which electrode is used for mild steel?

A close coupled electric motor, or an internal combustion engine rotates the armature in the generator.