Question

The pitch of a screw gauge is 0.5 mm and there are 100 divisions on it circular scale. The instrument reads + 2 divisions when nothing is put in between its jaws. In measuring the diameter of a wire, there are 8 divisions on the main scale and 83rd division coincides with the reference line. Then the diameter of the wire is

• A. $4.05mm$
• B. $4.405mm$
• C. $43.05mm$
• D. $1.25mm$

Answer 1

The correct option is B $4.405mm$

$\begin{array}{c}\text{Least count of screw gauge}=\frac{0.5mm}{100}=0.005mm\\ \text{Zero error}=2\times \left(L.C.\right)=0.01mm\\ \text{Sorew gauge reading}\\ \begin{array}{cc}\text{M.S.D.}& =0.5mm.\\ & =4.415\end{array}\end{array}$

$\begin{array}{cc}\text{Diameter of wire}& =4.415\text{- Zero error}\\ & =4.415-0.01\\ & =4.405mm\end{array}$