1. Measure the diameter of a small spherical/cylindrical body using Vernier callipers.

Aim:- To measure diameter of a small spherical/cylindrical body using Vernier callipers.

Apparatus:- Vernier callipers, a spherical body (pendulum bob) or a cylinder and a magnifying lens.

Theory:-

     If with the body between the jaws, the zero of Vernier scale lies ahead of N^th division of main scale, then main scale reading (M.S.R) = N.

     If nth division of Vernier scale coincides with any division of main scale, then Vernier scale reading (V.S.R) 

                = n x (L.C.) (L.C. is least count of Vernier callipers)

                = n x (V.C.) (V.C. is Vernier constant of Vernier callipers)

Total reading, T.R    = M.S.R + V.S.R (L.C. = V.C.)

                                 =N+ n x (V.C)

Vernier callipers - Measuring diameter of a sphere.

Observations:-

Determination of Vernier Constant (Least Count) of the Vernier Callipers-             1 M.S.D = 1mm

                           1O V.S.D = 9 M.S.D

Therefore,            1 V.S.D = M.S.D = 0.9 mm.

Vernier Constant,

V.C = 1 M.S.D - 1 V.S.D = (1 — 0.9) mm = 0.1 mm = 0.01 cm.

 

Zero error (i) ...... cm, (ii)..... cm, (iii) ...... cm.
Mean zero error (e) = ...... cm.
Mean zero correction (c) = - e = ...... cm.

Table for the Diameter (D):-

Serial Number	Main Scale Reading	Vernier Scale Reading		Total Reading
		No. of Vernier division coinciding	Value             [n x (V.C)]	Observed  n x V.C	Corrected  D = Do + C
1					D1
2					D2
3					D3
4					D4
5					D5
6					D6

Calculation:-

Mean corrected diameter (D) = D₁ + D₂ + D­₃ + D₄ + D₅ + D₆ / 6

Result:-

The diameter of the given sphere/cylinder is ...... cm.

Precautions:-

1. Motion of Vernier scale on main scale should be made smooth (by oiling if necessary).
2. Vernier constant and zero error should be carefully found and properly recorded.
3. The body should be gripped between the jaws firmly but gently (without undue pressure on it from the jaws).
4. Observations should be taken at right angles at one place and taken at least as three different places.

Sources of Error:-

1. The Vernier scale may be loose on main scale.
2. The jaws may not be at right angles to the main scale.
3. The graduations on scale may not be correct and clear.
4. Parallax may be there in taking observations.