When a conductor possesses a net electric charge, an electric field exists in the space the conductor. If the conductor carries a current, the region surrounding the conductor contains a magnetic field. If the charge or current varies with time, sociated fields at any point in the surrounding space will also vary at is, they will shrink and grow in magnitude in proportion to the strength of their source. In the near regions by the conductor, these fields will pulsate in synchronization with the time variation o the current or charge. Such synchronous fields are known as the near (or induction) fields. Capacitive and inductive interference signals are caused by such near fields. At points far from the conductor, the near electric and magnetic fields become negligible and plane-wave propagation of electromagnetic energy takes over. This re gion is called the far field. Radiated electromagnetic waves can cause ac signals of the same frequency as their originating source in any suitable conductors they encounter Such induced signals are thus called electromagnetic interference. Interference signals in ground loops can arise from near-field effects and far-field effects, as well as other electrical phenomena