|In the UK a typical power cct. the sockets are fed from two sides as it were. The power cct. wiring is in effect a ring of cable around the area and both ends of the ring connect to the same cct.. breaker/fuse.. Occasionally a radial cct. may be installed which is simply a single run of cable which feeds a string of outlets.|
Neither cct. also feed ceiling lighting directly. Those (lighting) ccts. are simply radial ccts - with no cross/interconection to power ccts.
In Canada/USA the standard is a series of radial ccts.; each of which is usually a mix of power and lighting...; and certain factors determine the mix of power outlets and lighting points on each radial (aka load balancing).
Any power outlat on the same phase (of mains services) can act as a network point with an appropriate adapter; even across separate "rings" or "radials". If there an RCD/GFI involved on any cct. this may impact (negatively) on the use of "lan over mains"/power-line adapters.
This RCD/GFI issue can be (frequently is) a problem in Canada/USA situations; less so an issue in the UK.
In the UK one can have (legally) a split system as it were. Some power outlets protected by an RCD/GFI, and some not so. Typically those not so protected might be fridge freezer outlets, central heating, and outlets servicing critical IT equipment; and one can also have some/all lighting ccts. in this grouping. Those so protected would serve all outdoor outlets, and general indoor outlets other than those as immediately above. My home (in the UK) has a split system; soho equipment, fridge freezer, central heating and indoor lighting are on not on an RCD/GFI.
This link shows the ring main system of wiring - a system considered by many to be more flexible, safer/safest, and also cost effective. It does not of course show an RCD/GFI - which would replace the standard main disconnect switch in a given consumer unit/cct. breaker (fuse) box/panel.