Exams › JEE Main › Physics

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

1. A is not correct but R is correct.
2. Both A and R are correct and R is the correct explanation of A.
3. A is correct but R is not correct.
4. Both A and R are correct and R is NOT the correct explanation of A.

Correct answer: A is not correct but R is correct.

Solution

The assertion is incorrect because the least count calculated from the given data is actually 0.01 mm, not 0.001 cm. However, the reason is correct as it accurately describes how to calculate the least count using the pitch and total divisions on the circular scale.

Related JEE Main Physics questions

• A body has a measured mass of \(5.00 \pm 0.05\) kg and a measured volume of \(1.00 \pm 0.05\) m\(^3\). What is the maximum possible percentage error in its density?
• A substance has a density of 4 g/cm\(^3\) in the CGS system. If a new unit system is used where the unit of length is 10 cm and the unit of mass is 100 g, what is the numerical value of the density in that system?
• Which of the following physical quantities has dimensions that do not match the other three?
• If the percentage uncertainties in measuring mass \(M\), length \(L\), and time \(T\) are 1%, 1.5%, and 3% respectively, what is the percentage error in a quantity having dimensions \(M L^{-1} T^{-1}\)?
• If \(E\), \(m\), \(J\), and \(G\) denote energy, mass, angular momentum, and the gravitational constant, respectively, then the dimensional formula of \(EJ^2/(m^5G^2)\) is identical to that of which quantity?
• A rod was found to have a measured length of 3.50 cm. Which measuring device was used for this reading?

⚔️ Practice JEE Main Physics free + battle 1v1 →