Physics VERNIER CALIPER

Vernier Caliper

Vernier calipers, an instrument for making very accurate linear measurements was introduced in 1631 by Pierre Vernier of France. Vernier calipers are widely used in scientific laboratories and in manufacturing for quality control measurements.

`text(Uses of a vernier calipers)`

Vernier calipers are used to measure

(i)The length of a rod or any object
(ii)The diameter of a sphere
(iii)The internal and external diameter of a hollow cylinder
(iv)The depth of a small beaker

The main parts of Vernier Calipers are ;

`text(Main Scale -)` The main scale is similar to that on a ruler, graduated in mm and cm on one side ; inches on the other side.

`text(Vernier Scale -)` The vernier scale is a sliding scale. It slides parallel to the main scale and enables readings to be made to a fraction of a division on the main scale.

`text(Screw -)` The vernier scale can be fixed at any position on the main scale with the help of a screw.

`text(Jaws -)` It has two jaws. The lower jaws are called outside jaws and they are used to measure the length of a rod ,diameter of a sphere or the external diameter of a cylinder. The upper jaws are called the inside jaws which are used to measure the internal diameter of a hollow cylinder or pipe .

`text(Strip -)` The thin strip is used to measure the depth of the objects like beakers.

Principle of Vernier

The graduations on the vernier scale are such that the length of ‘ n’ divisions on the vernier scale is equal to (n-1) divisions of the main scale.

Generally, a vernier has 10 divisions and the the length of these 10 divisions is equal to the length of 10 – 1 = 9 divisions of the main scale.

That is , 10 div of vernier scale = 9 mm.

1 div of vernier scale = 9/10 mm

`text(Least Count of Vernier or Vernier Constant :)`
It is defined as the difference between the values of one main scale division and one vernier scale division.

`text(L.C.= Value of one main scale division - Value of one vernier scale division)`

= 1 mm – 9/10 mm = 1 mm – 0.9 mm = 0.1 mm or 0.01 cm

OR `text(L.C. =) text(Value of one main scale division) / text(Total number of divisions on vernier)`

= 1 mm / 10 = 0.1 mm or 0.01 cm

`text(How to use a Vernier caliper)`

`1)` The jaws are first gently closed on the object to be measured.
`2)` Note the main scale reading (M.S.R)
`3)` Note the division on vernier scale which coincides with any division of the main scale. Multiply this number of vernier division with the least count. This is the vernier scale reading(V.S.R)

Hence V.S.R = Vernier scale coincidence x Least count(L.C.)

`4)` Add the main scale reading to the vernier scale reading. This gives the observed length.

Hence, Observed Reading = Main scale reading + Vernier scale reading

`text(Observed reading = M.S.R + V.S.R)`

OR `text[Observed reading = M.S.R. + (Vernier scale coincidence x L.C.)]`

 
SiteLock