Why would a small amount of electricity be generated with no dc excitation?

A small amount of electricity can be generated without DC excitation due to the phenomenon of electromagnetic induction. When a conductor moves through a magnetic field, or when the magnetic field around a stationary conductor changes, an electromotive force (EMF) is induced. This can happen in various systems, such as in generators or even through residual magnetism in the system, allowing for the generation of small amounts of voltage without the need for external DC excitation.