Question

A screw gauge is having a pitch of $1mm$ and there are $100$ division on its circular scale.The zero of the circular scale lies $4$ divisions below the reference line. When a steel wire is placed between the jaws, two main scale divisions are clearly visible and $67$ division on the circular scale are observed. The diameter of the wire is

• A. $2.71mm$
• B. $2.65mm$
• C. $2.63mm$
• D. $2.67mm$

Answer 1

The correct option is C $2.63mm$

$\text{pitch}=\mathrm{lmm}$

$\begin{array}{cc}L\cdot c& =\frac{pitch}{noof\text{div on}C.S}\\ & =\frac{1}{100}\\ & =0.01mm\end{array}$

$\begin{array}{c}\text{(+)ive zero error.}\\ =0+4\times L.C\\ =0.04mm\end{array}$

$\begin{array}{cc}M\cdot S\cdot R& =2mm\\ C\cdot S\cdot R& =67\times L\cdot C\\ & =67\times 0.01\\ & =0.67mm\end{array}$

$\begin{array}{c}\text{Final reading}\\ \text{MSR + CSR - zero error}\\ =2+0.67-0.04\\ =2.63mm\end{array}$