First slide
Measurement
Question

The pitch of a screw gauge having 50 divisions on its circular scale is 1 mm. When the two jaws of the screw gauge are in contact with each other, the zero of the circular scale lies 6 divisions below the line of graduation. When a wire is placed between the jaws, 3 linear scale divisions are clearly visible while 31st division on the circular scale coincides with the reference line. Find diameter of the wire.

Moderate
Solution

 L C = Pitch  Number of divisions on circular scale 

=1 mm50=0.02 mm

Positive zero error =n1(LC)

e=6×0.02=0.12 mm

Linear scale reading =3 (pitch) =3 mm

Circular scale reading =n2(LC)=31×0.02

=0.62 mm

Measured diameter of wire =(3+0.62)mn

=3.62 mm

Actual diameter of wire

=3.62 mm-0.12 mm=3.50 mm

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