Question

The pitch of a screw gauge having 50 divisions on its circular scale is 1 mm. When the two jaws of the screw gauge are in contact with each other, the zero of the circular scale lies 6 divisions below the line of graduation When a wire is placed between the jaws, 3 linear scale divisions are clearly visible while 31${}^{st}$ division on the circular scale coincide with the reference line. The diameter of the wire is

• A. $3.62mm$
• B. $3.50mm$
• C. $3.5mm$
• D. $3.74mm$

Answer 1

The correct option is D $3.74mm$

$\begin{array}{cc}\text{Zero error}& =-6\times \frac{1}{50}mm=-0.12mm\\ \text{Least count}=0.02& mm\\ \text{Screw gauge reading}& =3+31\times 0.02mm\\ & =3.62mm\end{array}$

$\begin{array}{cc}\text{Diameter of wire}& =3.62\text{- Zeroerar}\\ & =3.62-(-0.12)\\ & =3.74mm\end{array}$