State the physical meaning and explain the safety function of each of the following features standard in domestic mains electricity systems:

(i) The outer PVC sheath of a flexible three-core cable.

(ii) A 3 A cartridge fuse installed in a mains plug.

(iii) The earth wire (green-and-yellow) connected to a metal casing.

(iv) An appliance designated as double insulated (Class II).

Residual Current Circuit Breakers (RCCBs) and Miniature Circuit Breakers (MCBs) have largely replaced traditional fuses in modern domestic consumer units.

Identify two distinct advantages of using a circuit breaker instead of a standard cartridge fuse.