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Question: Answered & Verified by Expert

Assertion A: If in five complete rotations of the circular scale, the distance travelled on the main scale of the screw gauge is 5 mm and there are 50 total divisions on a circular scale, then the least count is 0.001 cm.

Reason R:
Least Count = Pitch  Total divisions on circular scale 
In the light of the above statements, choose the most appropriate answer from the options given below.

PhysicsExperimental PhysicsJEE MainJEE Main 2021 (27 Jul Shift 1)
Options:
  • A A is not correct but R is correct.
  • B Both A and R are correct and R is the correct explanation of A.
  • C A is correct but R is not correct.
  • D Both A and R are correct and R is NOT the correct explanation of A.
Solution:
1067 Upvotes Verified Answer
The correct answer is: A is not correct but R is correct.

Least count = Pitch  total division on circular scale 
In 5 revolution, distance travel, 5 mm.

In 1 revolution, it will travel 1 mm.
So the least count =150=0.02

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