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 student measured the diameter of a small  steel ball using a screw gauge of least count $0.001\, cm.$ The main scale reading is $5\, mm$ and zero of circular scale division coincides with $25$ divisions above the reference level. If screw gauge has a zero error of $-0.004 \,cm,$ the correct diameter of the ball is

A student measured the diameter of a wire using a screw gauge with the least count $0.001\, cm$ and listed the measurements. The measured value should be recorded as

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 $=0.1 \,{cm}$.

In a vernier calliper, when both jaws touch each other, zero of the vernier scale shifts towards left and its $4^{\text {th }}$ division coincides exactly with a certain division on main scale. If $50$ vernier scale divisions equal to $49$ main scale divisions and zero error in the instrument is $0.04 \mathrm{~mm}$ then how many main scale divisions are there in $1 \mathrm{~cm}$ ?