The vernier scale of a travelling microscope has $50$ divisions which coincide with $49$ main scale divisions. If each main scale division is $0.5\, mm$, calculate the minimum inaccuracy in the measurement of distance.

Main scale division of vernier calliper is $1\ mm$ and vernier scale division are in $A.P. ; 1^{st}$ division is $0.95\ mm$ ; $2^{nd}$ division is $0.9\ mm$ and so on. When an object is placed between jaws of vernier calliper, zero of vernier lies between $3.1\ cm$ and $3.2\ cm$ and $4^{th}$ division of vernier coincide with main scale division. Reading of vernier is  ………. $cm$

A screw gauge of pitch $0.5\,mm$ is used to measure the diameter of uniform wire of length $6.8\,cm$, the main scale reading is $1.5\,mm$ and circular scale reading is $7$. The calculated curved surface area of wire to appropriate significant figures is $……cm^2$ . [Screw gauge has $50$ divisions on the circular scale]

A Vernier calipers has $1 \mathrm{~mm}$ marks on the main scale. It has $20$ equal divisions on the Vernier scale which match with $16$ main scale divisions. For this Vernier calipers, the least count is

Student $A$ and Student $B$ used two screw gauges of equal pitch and $100$ equal circular divisions to measure the radius of a given wire. The actual value of the radius of the wire is $0.322\, {cm}$. The absolute value of the difference between the final circular scale readings observed by the students $A$ and $B$ is …. .

[Figure shows position of reference $'O'$ when jaws of screw gauge are closed]

Given pitch $=0.1 \,{cm}$.