Question

In a vernier caliper, 10 vernier scale divisions are equal to 9 main scale divisions. One main scale division is 1 mm. The device has some zero error as shown in the figure (a). When a cylinder of diameter D is inserted between them, the reading of scale is shown in figure (b). Then, the diameter of the cylinder in cm is

Answer 1

$1VSD=\frac{9}{10}\times 1MSD=0.9mm$
$LS=1MSD-1VSD=1mm-0.9mm=0.1mm=0.01cm$
In figure (a), the 6th VSD is alligned with MSD. Therefore the zero error is $6\times LS=0.6mm=0.06cm$
In figure (b), the 4th VSD is alligned with MSD. Therefore the reading is $3cm+4\times \left(LS\right)=3.04cm$
Total reading = Actual reading - Error = 3.04 - 0.06 = 2.98 cm