Question

The main scale of a vernier calipers is calibrated in mm and 19 divisions of main scale are equal in length to 20 divisions of vernier scale. In measuring the diameter of a cylinder by this instrument, the main scale reads 35 divisions and $4^{th}$ division of vernier scale coincides with a main scale division. Find radius of cylinder.

Answer 1

To find the zero error of the vernier caliper
Vernier scale reading = 4 $\times 0.005cm=0.02cm$
Total reading = main scale reading + vernier scale reading
$=3.5cm+0.02cm$
$=3.52cm$
Diameter $=3.52cm$
Radius = ${}^1{/}_2$ x diameter = ${}^1{/}_2$ x 3.52 cm = 1.76 cm

or $17.6mm$