A) 80.0096cm
B) 80.0272 cm
C) 1cm
D) 25.2cm
Correct Answer: A
Solution :
Using the relation \[{{l}_{t}}={{l}_{0}}(1+\alpha t)\] \[=1\times [1+11\times {{10}^{-6}}\times (40{}^\circ -20{}^\circ )]\] \[=1.00022\text{ }cm\] Now, length of copper rod at\[40{}^\circ C\] \[{{R}_{t}}={{l}_{0}}(1+\alpha t)\] \[=80[1+17\times {{10}^{-6}}(40{}^\circ -20{}^\circ )]1\] \[=80.0272\text{ }cm\text{ }1\] Now, number of cms observed on the scale \[=\frac{80.0272}{1.00022}=80.0096\]You need to login to perform this action.
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