A brass scale is graduated at 10∘C. What is the true length of a zinc rod which measures 60.00 cm on this scale at 30∘C? Linear expansively of brass = 18×10−6K−1.
A
60.02 cm
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B
60.2 cm
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C
61.02 cm
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D
60.0002 cm
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Solution
The correct option is A 60.02 cm Sincethe scale is graduated at 10∘C, 1 cm of the scale at 10∘C = exactly 1 cm ∴1 cm of the scale at 30∘C =exactly(1+18×10−6×20)cm ∴60 cm of the scale at 30∘C =exactly60.00(1+36×10−5) =60.02cm