Experiment 1: To Determine the Least Count and Use of a Vernier Calipers
Aim:
To find the least count of a Vernier Calipers and use it to measure:
- The internal diameter,
- The external diameter, and
- The depth of a given cylindrical object.
Apparatus Required:
- Vernier Calipers
- A cylindrical object (e.g., a small metal or plastic tube)
- A ruler (for verification, optional)
Theory:
1. Vernier Calipers is a device used to measure small lengths more precisely than a normal scale.
It consists of:
- Main scale (in cm/mm)
- Vernier scale (movable)
2. Least Count (LC):
The least count is the smallest measurement that can be accurately read using an instrument.
Least Count Formula:
LC = 1 Main Scale Division (MSD) – 1 Vernier Scale Division (VSD)
OR
LC = (Smallest division on main scale) ÷ (Number of divisions on Vernier scale)
Procedure:
Step 1: Find Least Count
- Note: Usually,
- 1 MSD = 1 mm
- 10 VSD = 9 mm
- So, LC = (1 mm × 10 – 9 mm) ÷ 10 = 0.1 mm or 0.01 cm
Step 2: Measure External Diameter
- Place the object between the two outer jaws.
- Note the main scale reading (MSR) just before zero of the Vernier scale.
- Note the Vernier scale division (VSD) that coincides with any main scale line.
- Calculate:
Total reading = MSR + (VSD × LC)
Step 3: Measure Internal Diameter
- Insert the inner jaws into the hollow part of the cylinder.
- Repeat the same steps as above to get the internal diameter.
Step 4: Measure Depth
- Use the depth rod of the Vernier.
- Place the base on the rim and extend the rod into the object.
- Take MSR and VSD again, and calculate total depth.
Observations Table:
| Measurement | MSR (cm) | VSD | LC (cm) | Final Reading (cm) |
|---|---|---|---|---|
| External Diameter | 0.01 | |||
| Internal Diameter | 0.01 | |||
| Depth of Cylinder | 0.01 |
Result:
- Least Count of the Vernier Calipers = 0.01 cm
- External Diameter = ___ cm
- Internal Diameter = ___ cm
- Depth = ___ cm
Precautions:
- Take readings at eye level to avoid parallax error.
- Ensure Vernier zero error is noted and corrected (if any).
- Close jaws gently to avoid damaging the object or instrument.