Sunday, November 13, 2011

TO USE A MICRO METER TO DETERMINE THE CROSS SECTION AREA OF A GIVEN GLASS ROD


      Radiant Higher Secondary School
Faculty of Science

EXPERIMENT NO: 1

OBJECT: TO USE A MICRO METER TO DETERMINE THE CROSS SECTION AREA OF A GIVEN GLASS ROD


APPARATUS REQUIRED:’

       1. MICROMETER SCREW
       2. GLASS ROD 

THEORY                
The screw gauge works on the principle of screw.
When we rotate the head ‘H’ by means of safety device ‘D’ through one complete rotation, the distance moved by the screw for every complete rotation is constant. This constant distance moved by the screw for one complete rotation of head ‘ H ‘ is called Pitch of the screw.If the head scale has 100 equal divisions, then the distance moved by the screw for even 1/100 of a complete rotation can be measured accurately,this is called Least count of screw gauge.
Therefore Least count (L.C) = . pitch/number of circular scale divisions 




OBSERVATION:

Value to 10 smallest division of main scale = 10 mm
Therefore, Value to 1 smallest division of main scale = 1 mm

In 4 complete rotations the circular scale moves through 4 divisions of main scale
Therefore, in 1 complete rotations the circular scale moves through 1 divisions of main scale

 Therefore , Pitch= 1 mm

Number of circular scale divisions (N) = 100
Least count (L.C) = pitch/number of circular scale divisions
                             = p/N
                             = 1/100 mm
                             = 0.01 mm

INSTRUMENTAL ERROR :


O of the circular scale is above or below or whole-side with the baseline of main scale by x divisions . Therefore instrumental error = ± x .LC(x multiplies L.C)
 Also , correction = (change the sign of the error , if its plus change to minus and if its minus then change to plus ) x .LC mm (x multiplies LC)

IN our case now , instrumental error = - 10 X 0.001 = - 0.01
                   Also    correction             = 0.01

OBSERVATION :

Sn.no
Main scale reading
x (mm)
Circular scale reading
y ( mm)
Value of circular scale reading
y.LC(y multiplies LC)
Total
x+y.LC(mm)
1
5
79
0.79
5.79
2
5
83
0.83
5.83
3
5
72
0.72
5.72
4
5
70
0.70
5.70
5
5
85
0.85
5.85
6
5
4
0.4
5.4
7
5
76
0.76
5.76
8
5
73
0.73
5.73

App mean of the data : 5.68
Correct mean of data :  5.78


CALCULATION:

Cross section of rod πd2 /4
                              = 26.25 mm2


RESULT : Hence , the cross section of rod found to be 26.25 mm2


PRECAUTIONS :

         In order to measure an object, the object is placed between anvil and spindle and circular is rotated using the ratchet until the object is secured. Do not handle and rotate circular. Hold the ratchet and turn until the object is lightly gripped.
1.  DO NOT OVERTIGHTEN BY THE CIRCULAR. Do not handle and rotate circular.
2.  Note that the ratchet knob must be used to secure the object firmly between anvil and spindle, otherwise the instrument could be damaged or give an inconsistent reading. The manufacturer recommends 3 clicks of the ratchet before taking the reading.
3.  The lock may be used to ensure that the circular does not rotate while you take the reading.

0 comments:

Post a Comment

Subscribe to: Post Comments (Atom)