Q63 / 90 · JEE Main 2024 (08 Apr Shift 2) · Physics

There are 100 divisions on the circular scale of a screw gauge of pitch $1 \mathrm{~mm}$. With no measuring quantity in between the jaws, the zero of the circular scale lies 5 divisions below the reference line. The diameter of a wire is then measured using this screw gauge. It is found that 4 linear scale divisions are clearly visible while 60 divisions on circular scale coincide with the reference line. The diameter of the wire is :

  • A
    $3.35 \mathrm{~mm}$
  • B
    $4.65 \mathrm{~mm}$
  • Correct answer
    C
    $4.55 \mathrm{~mm}$
  • D
    $4.60 \mathrm{~mm}$

Solution

$\begin{aligned} & \text { Least count }=\frac{1}{100} \mathrm{~mm}=0.01 \mathrm{~mm} \\ & \text { zero error }=+0.05 \mathrm{~mm} \\ & \text { Reading }=4 \times 1 \mathrm{~mm}+60 \times 0.01 \mathrm{~mm}-0.05 \mathrm{~mm} \\ & =4.55 \mathrm{~mm}\end{aligned}$

Hence, the correct answer is option: 'C'.

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