Question

Two full turns of the circular scale of a screw gauge cover a distance of `1mm` on its main scale. The total number of divisions on the circular scale is `50`. Further, it is found that the screw gauge has a zero error of `- 0.03mm`. While main scale reading of `3mm` and the number of circular scale divisions in line with the main scale as `35`. the dimeter of the wire is
A. (a) `3.32mm`
B. (b) `3.73mm`
C. ( c ) `3.67mm`
D. (d) `3.38mm`

Answer 1

Correct Answer - D
(d) Least count of screw gauge `= (0.5)/(50)mm = 0.01mm`
:. Reading `= [Main scale reading + circular scale reading xx L.C] - (zero error)`
`= [3 + 35 xx 0.01] - (-0.03) = 3.38mm`