Question

Screw gauge of pitch $0.1\text{cm}$ and $50$ divisions on circular scale measures thickness of an object. Which of the following measurement is possible for thickness?

• A. $2.123\text{cm}$
• B. $2.124\text{cm}$
• C. $2.125\text{cm}$
• D. $2.127\text{cm}$

Answer 1

The correct option is B $2.124\text{cm}$

Let $t$ be the thickness of the object.

So, reading of screw gauge taken as

$t=MSR+(n\times LC)$

Where,
$n$ is number of circular scale division lie over reference line
$MSR=$ Main scale reading
$LC=$ Least count of screw gauge

And we know that Least count of gauge is given as

$LC=\frac{\text{Pitch}}{\text{Number of division on circular scale}}$

$\Rightarrow LC=\frac{0.1}{50}=0.002\text{cm}$

Therefore, the digit at the third decimal place will be an even number.

Hence, option $\left(b\right)$ is correct.