Conductors, Insulators and Wiring Accessories
What this domain tests
Conductors, Insulators and Wiring Accessories tests wire sizes, insulation and colour codes, and the correct selection and connection of switches, sockets, holders, ceiling roses, plugs and distribution accessories.
Core rules
- Common copper conductor sizes are 1.0, 1.5, 2.5, 4.0 and 6.0 mm². Lighting circuits usually use 1.5 mm²; 16 A socket circuits use 2.5 mm²; heavy loads such as geysers and air-conditioners use 4.0 mm².
- Old Indian colour code: red, yellow and blue for phases, black for neutral, green for earth. Newer IS practice uses brown, black and grey for phases, blue for neutral, and green-with-yellow for protective earth.
- The switch must be in the phase conductor, not the neutral. A two-way switch has three terminals - common, L1 and L2 - and is used for stair-case control.
- Accessories are rated, for example 6 A and 16 A. A 6 A switch must not control a 16 A socket circuit.
- A ceiling rose supports the lamp flex and provides terminal connections; the earth continuity must be maintained to metal fittings.
- Insulators such as porcelain, bakelite and PVC separate live parts from touchable surfaces.
Worked example
For a 16 A socket outlet, select a 16 A socket, a 16 A MCB, 2.5 mm² copper conductors and a 30 mA RCCB. Connect the phase to the switch, the neutral to the socket neutral terminal, and the earth to the earth terminal. The switch breaks the phase, so the socket is dead when switched off.
Traps that cost marks
Switching the neutral; using a 6 A switch on a 16 A load; omitting the earth to a metal holder; and using a wire size chosen only by what fits the terminal.