Practical Workshop and Viva-Voce
Scope
The practical and viva test bench skills, measurement accuracy, wiring technique and your ability to explain why a job is done a particular way.
Core rules
- Bench tools: vice, files, hacksaw, taps and dies, drills, wire strippers, crimping tool, soldering iron. Use the correct file for the metal and clean the file with a card file, not by hand.
- Measurement: vernier calliper least count = 1 main-scale division/vernier divisions, typically 0.02 mm; micrometer least count = pitch/number of thimble divisions, typically 0.5/50 = 0.01 mm. Check and record zero error.
- Wiring practice: strip only the required length, avoid nicks in the conductor, crimp ferrules on stranded wire and route wiring neatly with slack at terminals.
- Testing sequence: continuity, insulation resistance, polarity, earth continuity, then energise.
- Viva answers should name the standard: IS 732 for wiring, IS 3043 for earthing, IS 694 for PVC wire, IE Rules 1956 for safety.
Worked example
A micrometer has a 0.5 mm pitch and a 50-division thimble. Least count = 0.5/50 = 0.01 mm. The sleeve reads 5.5 mm (5 mm plus one half-millimetre division) and the thimble reads 23. Measurement = 5.5 + (23 × 0.01) = 5.73 mm. If the zero error were +0.02 mm, the corrected reading would be 5.73 − 0.02 = 5.71 mm. Recording the zero error and the correction separately is what earns full marks.
Traps that cost marks
Ignoring zero error, fitting a hacksaw blade with teeth facing backwards, making a cold solder joint and then covering it with insulation, and energising a circuit before the insulation test. In viva, answer with the standard and the reason, not just the name of the tool.