Page 22 - Physics - XI

d
d d
d
Mean observed diameter = d = 1 2 3 4 = ______ mm
0
4
Mean corrected diameter = d = d + (– e) = ______ mm
0
Table for the calculation of the thickness (t) of the sheet
S. No. Linear scale No. of circular scale Circular scale reading Observed thickness
reading divisions coinciding y = n × V.C. t = x + y
i
x (n) (mm) (mm)
(mm)
1.

2.

3.

4.

t
t
Mean observed thickness = t = t ++ + t 4 = ______ mm
1
3
2
0
4
Mean corrected thickness = t = (t + zero correction)
0
t = ______ mm = ______ cm
Result
1. The diameter of the given wire is ______ cm.

2. The thickness of the given sheet is ______ cm.

Precautions

1. The screw should be free from friction. It should be oiled if it is needed.
2. The screw should be always turned by ratchet and not by cap to avoid excess pressure.

3. Zero correction must be noted with proper sign and added algebraically.
4. The screw should be moved in the same direction for the same set of observations to avoid the backlash
error.
5. Stop turning the ratchet when it starts slipping.
6. Take the reading of the diameter in two mutually perpendicular directions.
7. Error due to parallax should be avoided.

Sources of Error

1. The screw gauge may have backlash error.
2. The screw may have friction.
3. The divisions on linear scale and circular scale may not be evenly spaced.

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