Two full turns of the circular scale of a screw gauge cover a distance of 1 mm on its main scale. Th

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 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\

Professor PC Thomas Classes · Answer

(a) : Least count of the screw gauge $=\frac{0.5 \mathrm{~mm}}{50}=0.01 \mathrm{~mm}$\ Main scale reading $=3 \mathrm{~mm}$. Vernier scale reading $=35$\ $	herefore$ Observed reading $=3+0.35$\ $=3.35$ zero error $=-0.03$\ $	herefore$ actual diameter of the wire\ $=3.35-(-0.03)=3.38 \mathrm{~mm}$.\