JEE Main & Advanced Physics Mathematical Tools, Units & Dimensions JEE PYQ - Mathematical Tools Units and Dimensions

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 circular scale is 50. Further, it is found that screw gauge has a zero error of - 0.03mm. While measuring the diameter of a thin wire, a student notes the main scale reading of 3mm and the number of circular scale divisions in line with the main scale as 35. The diameter of wire is [AIEEE 2008]

A) 3.67 mm

B) 3.38 mm

C) 3.32 mm

D) 3.73 mm

Correct Answer: B

Solution :

[b] Least count \[=\frac{0.5\,mm}{50}=0.01mm\]

Zero error = - 0.03 mm

Measured diameter = 3 mm + 35 \[\times \] 0.01 mm = 3.35 mm

Corrected diameter = 3.35 mm - (- 0.03mm) = 3.38 mm