Question

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 thin wire, a student notes down 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 :

• A. 3.67 mm
• B. 3.38 mm
• C. 3.32 mm
• D. 3.73 mm

Answer 1

The correct option is B 3.38 mm

M.S.R. $=3mm$
No. of circular divisions $=35$
Since 100 divisions $=1mm$
1 division $=0.01mm$
So, 35 division $=0.35mm$
Since zero error is $=-0.03mm$
It will add up in the measurement,
$\Rightarrow 3+0.35+\left(0.03\right)=3.38mm$