JEE Main & Advanced Physics Mathematical Tools, Units & Dimensions JEE PYQ - Mathematical Tools Units and Dimensions

  • question_answer
    In a screw gauge, 5 complete rotations of the screw cause it to move a linear distance of 0.25cm. There are 100 circular scale divisions. The thickness of a wire measured by this screw gauge gives a reading of 4 main scale divisions and 30 circular scale divisions. Assuming negligible zero error, the thickness of the wire is: [JEE Online 15-04-2018]

    A)       \[0.0430cm\]

    B) \[0.3150cm\]

    C) \[0.4300cm\]

    D) \[0.2150cm\]

    Correct Answer: D

    Solution :

    [d] In one rotation scale moves
    \[\frac{0.25}{5}=0.05cm\]
    Least count \[=0.05\times {{10}^{-2}}cm\]
    For 4 main scale division \[=4\times 0.05=0.2cm\]
    For circular scale division
    \[=30\times 0.05\times {{10}^{-2}}=1.5\times {{10}^{-2}}cm\]
    Thickness of wire\[=0.2+0.015=0.2150cm\]


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