Least count of one big division on main scale is
By BYJU'S Exam Prep
Updated on: September 25th, 2023
A transit’s main plate is divided into 1080 equal segments. The vernier’s 60 divisions exactly match the main plate’s 59 divisions. The transit can read angles accurate up to-
- 5″
- 10″
- 15″
- 20″
- 30″
Table of content
Answer: D. 20
Least count of one big division on main scale is 20.
Solution:
Least count of one big division on the main scale(S) = Length of one big division/Total number of divisions
Least count of a vernier scale is equal to the difference in length of one division of the main scale and one division of the vernier scale.
In a direct vernier (n-1) division of the main scale is equal to the n divisions on the vernier scale. Thus,
n.v=(n-1).S
v={(n-1)/n}S
Least count is given as,
L.C. = S-v
L.C. = S-{(n-1)/n}S
L.C. = S/n
Given: Total no. of divisions on main scale = 1080
Length of one division = 360º/1080
n= 60
L.C. = {(360º/1080)/60}×3600=20
