Experimental Physics

JEE Main level, single correct, medium

37 of 70

Question 37 of 70

In a Screw Gauge, fifth division of the circular scale coincides with the reference line when the ratchet is closed. There are 5050 divisions on the circular scale, and the main scale moves by 0.5mm0.5mm on a complete rotation. For a particular observation the reading on the main scale is 5mm5mm and the 20th{20}^{\text{th}} division of the circular scale coincides with reference line. Calculate the true reading.

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Answer: (C) 5.15mm5.15mm

L.C. of screw Gauge=0.550=0.01mm=\dfrac{0.5}{50}=0.01mm
Zero error of screw Gauge =5×L.C.=5\times L.C.=5×0.01=0.05mm=5\times 0.01=0.05mm
Reading of screw gauge == main scale reading ++ circular scale reading ×L.C.−\times L.C.-Zero error =5+(20×0.01)−0.05=5.15mm=5+\left(20\times 0.01\right)-0.05=5.15mm

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