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Vernier calipers: internal/external diameter and vessel depth: NEET MCQs with answers

75 questions on this topic of Experimental Skills (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.

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easy

1. The pitch of a main scale of a vernier calliper is 0.5 mm. If n divisions of the vernier scale coincide with (n - 1) divisions of the main scale, what is the least count of the vernier calliper in mm?

  1. n / 0.5
  2. 0.5 / (n - 1)
  3. 0.5 / n
  4. 0.5 × n
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Answer: (C) 0.5 / n

Least count = 1 MSD - 1 VSD. Given n VSD = (n - 1) MSD, so 1 VSD = ((n - 1)/n) MSD. Therefore, LC = 1 MSD × [1 - (n - 1)/n] = (1 MSD)/n. Since 1 MSD = 0.5 mm, LC = 0.5 / n mm.

medium

2. A vernier calliper has 1 MSD = 0.5 mm and 50 vernier scale divisions equal to 45 main scale divisions. What is the least count of this calliper?

  1. 0.01 mm
  2. 0.02 mm
  3. 0.05 mm
  4. 0.10 mm
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Answer: (C) 0.05 mm

1 VSD = (45 / 50) MSD = 0.9 MSD. Least count = 1 MSD - 1 VSD = (1 - 0.9) MSD = 0.1 MSD = 0.1 × 0.5 mm = 0.05 mm.

hard

3. A vernier calliper has 1 MSD = 0.5 mm. 16 vernier scale divisions coincide with 15 main scale divisions. Before making a measurement, when the jaws are closed, the 0 mark of the vernier scale is to the left of the main scale zero, and the 12th vernier division aligns with a main scale line. When measuring the external diameter of a cylinder, MSR is 2.5 mm and the 8th VSD coincides. The true diameter is:

  1. 2.625 mm
  2. 2.875 mm
  3. 2.750 mm
  4. 3.000 mm
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Answer: (B) 2.875 mm

LC = 1 MSD - 15/16 MSD = (1/16) × 0.5 mm = 1/32 mm = 0.03125 mm. Since the vernier zero is to the left, it has a negative zero error: Zero Error = -(16 - 12) × LC = -4 × (1/32) mm = -0.125 mm. Observed reading = 2.5 mm + 8 × (1/32) mm = 2.5 mm + 0.25 mm = 2.75 mm. True diameter = Observed - Zero Error = 2.75 mm - (-0.125 mm) = 2.875 mm.

medium

4. In a vernier calliper, 20 vernier divisions coincide with 19 main-scale divisions of 1 mm each. The main-scale reading is 32 mm and the 15th vernier division coincides with a main-scale division. The measured length is:

  1. 3.35 cm
  2. 3.2 cm
  3. 3.125 cm
  4. 3.275 cm
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Answer: (D) 3.275 cm

Least count = 1 MSD − 1 VSD = 1/20 mm = 0.05 mm. Reading = 32 + 15 × 0.05 = 32.75 mm = 3.275 cm.

easy

5. In a vernier calliper, 1 main scale division is 1 mm. If 25 vernier scale divisions coincide with 24 main scale divisions, what is the least count of the instrument?

  1. 0.01 mm
  2. 0.02 mm
  3. 0.04 mm
  4. 0.05 mm
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Answer: (C) 0.04 mm

Least count (LC) = 1 MSD - 1 VSD. Since 25 VSD = 24 MSD, 1 VSD = (24/25) MSD. Therefore, LC = (1 - 24/25) MSD = (1/25) mm = 0.04 mm.

hard

6. The main scale of a vernier calliper has divisions in millimeters. When measuring the external diameter of a sphere, the main scale reads 2.8 cm and the 4th vernier division aligns with a main scale line. If 40 vernier divisions coincide with 38 main scale divisions, what is the measured diameter?

  1. 2.840 cm
  2. 2.810 cm
  3. 2.820 cm
  4. 2.805 cm
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Answer: (C) 2.820 cm

1 MSD = 1 mm. 40 VSD = 38 MSD = 38 mm, so 1 VSD = 38/40 mm = 0.95 mm. Least count = 1 MSD - 1 VSD = 1 mm - 0.95 mm = 0.05 mm = 0.005 cm. Measured diameter = MSR + (VSR × LC) = 2.8 cm + (4 × 0.005 cm) = 2.8 cm + 0.020 cm = 2.820 cm.

easy

7. Statement I: When the jaws of a vernier calliper are closed, if the zero mark of the vernier scale lies to the right of the main scale zero mark, the zero error is positive. Statement II: A positive zero error is always added to the observed reading to obtain the true reading.

  1. Statement I is true, Statement II is false
  2. Both Statement I and Statement II are true
  3. Statement I is false, Statement II is true
  4. Both Statement I and Statement II are false
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Answer: (A) Statement I is true, Statement II is false

When the vernier zero lies to the right of the main scale zero, the instrument reads a value greater than zero even when jaws are closed, which is a positive zero error. True reading = Observed reading - (Zero Error), so a positive zero error is always subtracted, making Statement II false.

easy

8. While measuring the internal diameter of a hollow metal cylinder using the upper jaws of a vernier calliper, the main scale reads 3.2 cm and the 4th vernier division coincides with a main scale mark. The instrument has 1 MSD = 1 mm and 10 vernier divisions equal 9 MSD. If the calliper has a zero error of +0.03 cm, what is the corrected internal diameter?

  1. 3.18 cm
  2. 3.24 cm
  3. 3.27 cm
  4. 3.21 cm
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Answer: (D) 3.21 cm

The least count LC = 1 mm - 0.9 mm = 0.1 mm = 0.01 cm. Observed reading = MSR + (VSR × LC) = 3.2 cm + (4 × 0.01 cm) = 3.24 cm. Corrected reading = Observed reading - Zero error = 3.24 cm - (+0.03 cm) = 3.21 cm.

medium

9. In a vernier calliper, 10 vernier divisions coincide with 9 main-scale divisions of 1 mm each. The main-scale reading is 54 mm and the 7th vernier division coincides with a main-scale division. The measured length is:

  1. 6.1 cm
  2. 5.4 cm
  3. 5.47 cm
  4. 5.33 cm
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Answer: (C) 5.47 cm

Least count = 1 MSD − 1 VSD = 1/10 mm = 0.1 mm. Reading = 54 + 7 × 0.1 = 54.7 mm = 5.47 cm.

medium

10. In a vernier calliper, 10 vernier divisions coincide with 9 main-scale divisions of 1 mm each. The main-scale reading is 59 mm and the 4th vernier division coincides with a main-scale division. The measured length is:

  1. 5.9 cm
  2. 5.86 cm
  3. 6.3 cm
  4. 5.94 cm
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Answer: (D) 5.94 cm

Least count = 1 MSD − 1 VSD = 1/10 mm = 0.1 mm. Reading = 59 + 4 × 0.1 = 59.4 mm = 5.94 cm.

easy

11. While measuring the internal diameter of a tube using upper jaws, which of the following practices is essential to obtain the correct diameter?

  1. Measure along the chord of the cross-section rather than through the center
  2. Tilt the jaws at an acute angle to the axis of the cylinder
  3. Apply maximum possible pressure to bend the internal jaws slightly
  4. Keep the jaws oriented at the maximum opening achievable along the diameter
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Answer: (D) Keep the jaws oriented at the maximum opening achievable along the diameter

The upper jaws must span the true diameter of the circular cross-section, which represents the maximum distance between two points on the inner boundary. Tilting or placing them along a chord gives an incorrect, smaller value.

medium

12. In a vernier calliper, 10 vernier divisions coincide with 9 main-scale divisions of 1 mm each. The main-scale reading is 50 mm and the 2nd vernier division coincides with a main-scale division. The measured length is:

  1. 5.02 cm
  2. 5.2 cm
  3. 5 cm
  4. 4.98 cm
Show answer and explanation

Answer: (A) 5.02 cm

Least count = 1 MSD − 1 VSD = 1/10 mm = 0.1 mm. Reading = 50 + 2 × 0.1 = 50.2 mm = 5.02 cm.

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