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In a vernier calliper, when both jaws touch each other, zero of the vernier scale shifts towards left and its $4^{\text {th }}$ division coincides exactly with a certain division on main scale. If $50$ vernier scale divisions equal to $49$ main scale divisions and zero error in the instrument is $0.04 \mathrm{~mm}$ then how many main scale divisions are there in $1 \mathrm{~cm}$ ?
$40$
$5$
$20$
$10$
Solution
$4^{\text {th }}$ division coincides with $3^{\text {rd }}$ division then
$ 0.004 \mathrm{~cm}=4 \mathrm{VSD}-3 \mathrm{MSD}$
$49 \mathrm{MSD}=50 \mathrm{VSD}$
$1 \mathrm{MSD}=\frac{1}{\mathrm{~N}} \mathrm{~cm}$
$0.004=4\left\{\frac{49}{50} \mathrm{MSD}\right\}-3 \mathrm{MSD}$
$0.004=\left(\frac{196}{50}-3\right)\left(\frac{1}{\mathrm{~N}}\right)$
$\mathrm{N}=\frac{46}{50} \times \frac{1000}{4}=\frac{46 \times 1000}{200}=230$
Similar Questions
Area of the cross-section of a wire is measured using a screw gauge. The pitch of the main scale is $0.5 mm$. The circular scale has 100 divisions and for one full rotation of the circular scale, the main scale shifts by two divisions. The measured readings are listed below.
Measurement condition | Main scale reading | Circular scale reading |
Two arms of gauge touching each other without wire | $0$ division | $4$ division |
Attempt-$1$: With wire | $4$ division | $20$ division |
Attempt-$2$: With wire | $4$ division | $16$ division |
What are the diameter and cross-sectional area of the wire measured using the screw gauge?