Electrical Drawing, Symbols and Wiring Diagrams
What this domain tests
Electrical Drawing, Symbols and Wiring Diagrams tests reading and producing layouts, schematics and wiring diagrams using standard symbols.
Core rules
- A single-line diagram shows the supply, DB, protective devices and circuits as single lines; it is used for planning and fault tracing.
- A schematic shows electrical logic - how devices are connected - without regard to physical position. A wiring diagram shows the actual terminal-to-terminal connections. A layout shows positions on the wall or board.
- Learn common symbols: switch, two-way switch, socket, lamp, fan, ceiling rose, MCB, RCCB, earth, motor, resistor, capacitor and bell.
- The title block, legend and scale must be read before the drawing. A symbol that is not in the legend is not assumed.
- Polarity matters: the switch is shown in the phase conductor, and the neutral is continuous to the load.
- Keep drawings legible: labelled conductors, cable sizes, circuit numbers and earth connections.
Worked example
A stair-case light is controlled from two points. The drawing shows the phase feed to the common terminal of the first two-way switch; L1 and L2 run as strappers to L1 and L2 of the second switch; the common of the second switch goes to the lamp; the lamp neutral returns to the DB. Either switch toggles the lamp.
Traps that cost marks
Confusing a two-way switch with a two-pole switch; drawing the switch in the neutral; ignoring the legend; and producing a schematic when the question asks for a wiring layout.