This modular coil ... generator applications, and features a 3D printed structure to wind your copper about as well as a series of ferromagnetic machine screws and nuts meant to boost the field ...

Magnets are also surrounded by a similar three-dimensional field ... along the lines of magnetic force surrounding the magnet. The simplest generator consists of just a coil of wire and a bar ...

and is often referred to as the generator ... a magnetic field around itself. Note that this magnetic field opposes the original change. For example, if a magnet is moved into a coil of wire ...