If you’ve ever opened an electrical box and wondered if it is the end-of-run circuit or does this circuit continue on, here’s the way to know. If you look in the box and it has only one bale coming into it, you’ve got an end-of-run circuit. This could be a lighting run where the feed starts out at the electrical panel, via a circuit breaker, and continues through a light fixture box, and then on to the switch box. In this case, the final cable run from the light box to the switch box carries the hot feed (the black wire) and the switch leg (the white wire). In this example, the neutral is connected to the light in the switch box. The other end of the white wire is connected to the neutral buss in the electrical panel.
In review, the simple explanation of an end-of-run circuit is the last device on that circuit, regardless of whether it is a switch, outlet or an appliance connection. This is not to be confused with a middle-of-run circuit.