Mechanical / Civil Lab Viva

In an Indian engineering college, every lab course ends in a practical examination where the student performs one experiment or writes one program and then faces a viva voce from an internal examiner and, in the end-semester university exam, an external examiner appointed by the university. The viva typically lasts five to fifteen minutes per student, and the examiner opens the lab record or the just-completed experiment and asks the student to explain the setup, the readings, the theory behind them and what would change if a condition changed. The final-year project viva is longer: a panel of the guide, an internal examiner and an external examiner, often from industry, hears a presentation and demo and then questions each team member on the problem, design choices, their own module and the results. Marks for the viva are set by the university scheme and usually form a part of the practical or project marks, with the exact split varying by university. The ExamPilot mock compresses this into a twelve-minute viva with one examiner who opens your record, probes one subject in depth, tests what-if reasoning on a scenario from the lab or project, and closes without revealing marks.

1. 1

   Strength of materials

   In the tensile test on the UTM, why does the mild steel specimen neck before it breaks, and how did you locate the yield point on your graph?

   What a strong answer covers

   Necking begins after the ultimate load when deformation concentrates in one region and the cross-section shrinks; the yield point is read from the drop or plateau after the linear region, or by the 0.2 percent offset method if there is none. Avoid confusing ultimate stress with breaking stress.

2. 2

   Fluid mechanics

   In the Reynolds apparatus, how did you decide whether the flow was laminar or turbulent, and show me how you calculated the Reynolds number from your readings.

   What a strong answer covers

   Describes the dye filament staying straight, wavering or mixing, then computes velocity from discharge and pipe area and the Reynolds number using diameter and kinematic viscosity, with units shown. Avoid quoting a number from the manual instead of your own readings.

3. 3

   Measurement

   Your vernier caliper reads 0.02 mm below zero when the jaws are closed. What is this error called, and how did you correct your readings?

   What a strong answer covers

   Identifies a negative zero error, explains that the correction is added to each observed reading, and distinguishes it from least count, which is the smallest division the instrument can read. Avoid applying the correction with the wrong sign.

4. 4

   Concrete technology

   Your concrete mix showed a collapse slump in the lab. What does that tell you, and what would you change in the mix?

   What a strong answer covers

   A collapse slump suggests a very wet or lean mix with poor cohesion, risking segregation and lower strength; remedies include reducing water, checking the water-cement ratio, aggregate grading or using a plasticiser rather than adding water. Avoid assuming a high slump is good workability.

5. 5

   Surveying

   In your levelling field book, explain the purpose of the back sight and fore sight, and how you checked your arithmetic.

   What a strong answer covers

   The back sight on a known level fixes the height of instrument, fore sights give reduced levels of new points, and the check is that the difference between sums of back sights and fore sights equals the difference between the last and first reduced levels. Avoid skipping the arithmetic check.

6. 6

   Thermal engineering

   In the IC engine test rig, how did you calculate brake power from your dynamometer readings, and why is mechanical efficiency always below one?

   What a strong answer covers

   Uses torque from load and arm length with engine speed to get brake power, compares it with indicated power, and explains losses from friction, pumping and auxiliaries. Avoid unit mistakes between kilowatts, revolutions per minute and radians per second.

7. 7

   Engineering drawing

   Look at this drawing sheet. A hidden edge is drawn as a continuous thick line and the dimension is placed inside the view. What is wrong, and why does it matter?

   What a strong answer covers

   Hidden edges should be thin dashed lines and dimensions should generally sit outside the view with proper extension lines, because a workshop reads conventions literally and can make the part wrong. Avoid dismissing line types as cosmetic.

8. 8

   Sources of error

   In the hydraulic jump or notch experiment, your measured discharge coefficient differed from the textbook value. Name the errors you actually noticed in the lab.

   What a strong answer covers

   Specific observed issues such as unsteady head reading, a leaking measuring tank, timing errors with the stopwatch or the notch not being sharp, and what was done to reduce each. Avoid a generic list of personal, instrumental and parallax errors with no link to the experiment.

9. 9

   Standards

   Concrete cubes are usually crushed after one week and again after four weeks of curing. What does each result tell the site engineer, and what size of cube did you test?

   What a strong answer covers

   Explains that strength develops with hydration, 28-day strength is the design reference and 7-day results give an early indication; standard cubes are 150 mm, cured in water before testing. A strong answer mentions the relevant IS code only if sure. Avoid guessing code numbers.

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