In an isolated generator connected only to a grounding electrode with no other circuit completion, current will not flow into the ground because there is no return path to the source.

An overhead power line conductor has three main phases that correspond to a rotating magnetic field in a three-phase generator, visible on nearly any transmission line.

Ground return current and other natural phenomena in the ground (lightning, telluric currents) 'kind of mix together' below the surface, and the exact flow patterns are more complicated than simple line diagrams suggest.

Close to a ground electrode, the concentric shells are spaced tightly together toward a single point or line, creating high resistance; this spacing is related to soil resistivity and represents a serious safety issue.

Even bipolar (two-conductor) high voltage DC transmission lines often include grounding systems so they can use ground return during an outage or emergency if one pole is out of service.

Nichrome wire connected to mains voltage (with power resistors limiting current) heats up when electrical current flows through it, demonstrating that an electric potential difference exists at every point along the wire, as shown by measuring voltage at different locations.

Protective relays that monitor parts of the power grid detect problems by measuring fault current, and nearly all rely on fault current being much higher than normal electrical loads to distinguish between normal operation and short circuits.

Voltage is not a property of a single wire or location, but rather the difference in electrical potential between two points, which is why engineers arbitrarily assign a common reference point (ground) zero potential for measurement convenience.