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Two full turns of the circular scale of a screw gauge cover a distance of 1 mm 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 - 0.03 mm. While measuring the diameter of a wire, a student notes the main scale reading of 3 mm and the number of circular scale divisions in line with the main scale as 35. The diameter of the wire is
- 3.32 mm
- 3.73 mm
- 3.67 mm
- 3.38 mm
Correct answer: 3.38 mm
Solution
To find the diameter of the wire, we first calculate the least count of the screw gauge, which is 0.02 mm (1 mm/50 divisions). The reading from the main scale is 3 mm, and the circular scale reading contributes 0.70 mm (35 divisions x 0.02 mm). Adding these gives 3.70 mm, and accounting for the zero error of -0.03 mm results in a final measurement of 3.38 mm.
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