What phenomenon causes current to flow in circuits completed by earth's paths?

The phenomenon that causes current to flow in circuits completed by the earth's paths is induction. Induction occurs when a changing magnetic field near a conductor induces an electromotive force (EMF) within that conductor, leading to the flow of current. This is particularly relevant in the context of alternating currents (AC), where the direction of current changes frequently, resulting in magnetic fields that induce current in nearby conductors or in grounded systems.

In grounding systems, such as those used in electrical installations, induction is a crucial factor for ensuring safety and stability in the electrical flow by providing a path for fault currents to return to the ground. This helps prevent damage to devices and reduces the risk of electric shock. Therefore, induction is fundamental in understanding how current can flow through earth paths in various electrical systems.