Engineering Drawing
Engineering Drawing
This domain tests reading and producing electrical and PV drawings: orthographic views, scales, line types, dimensioning, symbols and single-line diagrams.
Core rules
- First-angle projection is standard in India: the object is between the observer and the plane, so the top view is placed below the front view and the left-side view on the right.
- Scale = drawing length / actual length. Common scales are 1:1, 1:10, 1:50 and 1:100.
- Visible edges use continuous thick lines; hidden edges use dashed lines; centre lines use chain lines; dimension lines are thin with arrowheads.
- Electrical single-line diagrams show generation, protection, isolation and load paths without drawing every conductor.
- PV symbols should identify module/string, DC isolator, charge controller, inverter, meter and earthing.
Worked example
A roof plan is drawn at 1:50. A cable route measures 80 mm on the drawing. Actual length = 80 × 50 = 4000 mm = 4.0 m. If the route must avoid a 1.5 m setback, that is 30 mm on the same drawing, so the scaled layout can be checked directly against the drawing.
Traps that cost marks
Using third-angle placement in a first-angle paper; measuring a scaled drawing without converting; confusing hidden and centre lines; omitting the DC isolator or earthing symbol from a PV single-line diagram; mixing mm and m in scale calculations.