In a vernier calliper, when both jaws touch each other, zero of the vernier scale shifts towards left and its 4th 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 mm then how many main scale divisions are there in 1 cm ?
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Question

In a vernier calliper, when both jaws touch each other, zero of the vernier scale shifts towards left and its 4th 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 mm then how many main scale divisions are there in 1 cm ?

Options

G1 Physics · Accepted Answer

The source notes that the 4th Vernier division coincides with the 3rd main-scale division. Given: 50 VSD = 49 MSD and the magnitude of zero error is: 0.04 mm = 0.004 cm Using the source relation: 0.004 = 4VSD - 3MSD and: VSD = (49/50)MSD we get: 0.004 = [4(49/50) - 3]MSD = (46/50)MSD Therefore: MSD = 0.004 × 50/46 cm The source gives the official NTA answer as Option C = 20 main-scale divisions per cm. Note: Allen marks this question as BONUS, while NTA answer is Option C.