Page 11 - Physics - XI

SECTION - A

1 Units and Measurements
Units and Measurements

EXPERIMENT - 1

Aim

To measure diameter of a small spherical/cylindrical body and to measure internal diameter and depth of a
given beaker/calorimeter using Vernier Callipers and hence fi nd its volume.

Apparatus and Materials Required

Vernier Calliper, a spherical body (pendulum bob) or a cylindrical body, a beaker, or a calorimeter

Description of the Measuring Device
The main parts of the Vernier Callipers are:

1. Main scale: The main scale M of Vernier Callipers is made of steel. It is graduated in mm and cm on
one side and inches and tenth of an inch on the other side. It consists of two fi xed jaws A and C at right
angle to the scale.
2. Vernier scale: The vernier scale V slides along the main scale M. It can be fi xed at any position with
the help of the screw S. Vernier scale has ten equal divisions. Ten divisions of the vernier scale are
equal to nine divisions of the main scale.

3. Movable jaws: It has two jaws B and D projected at right angle to the main scale. These two jaws are
called movable jaws.
C D
S

M
N
0 1 2 3 4 5 14 15

2 3

A B V
Fig. 1.1: Vernier Calliper

4. Strip: A strip N is attached to the vernier scale. This strip is used to measure the depths of the hollow
objects.
Principle/Theory

The diff erence between the values of one main scale division and one Vernier scale division is called
Vernier constant (V.C.) or the least count of the Vernier Callipers.
Let us consider that n Vernier scale divisions coincide with (n – 1) main scale divisions.
Hence, n Vernier scale divisions (V.S.D.) = (n – 1) main scale divisions (M.S.D.)

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