A Vernier caliper has 1 mm marks on the main scale. It has 20 equal divisions on the Vernier scale which match with 19 main scale divisions. When the measuring jaws are in contact, the zero of the Vernier scale is to the left of the zero of the main scale and the 12^ th Vernier division coincides with a main scale mark. When this caliper is used to measure the diameter of a cylinder, the main scale reading is 2.5 cm

Step-by-step solution

First, calculate the least count (LC) of the Vernier caliper. Value of 1 MSD = 1 mm . Since 20 VSD = 19 MSD , we have 1 VSD = 19 20 mm . LC = 1 MSD - 1 VSD = 1 mm - 19 20 mm = 1 20 mm = 0.05 mm = 0.005 cm . Next, determine the zero error. Since the Vernier zero is to the left of the main scale zero, the zero error is negative. Zero error = - ( Total VSD - n) LC Zero error = - (20 - 12) 0.005 cm = - 8 0.005 cm = -0.040 cm . Now, calculate the observed reading for the cylinder's diameter. Observed reading = Main scal