A) \[80.0096\,cm\]
B) \[80.0272\,cm\]
C) \[1\,cm\]
D) \[25.2\,cm\]
Correct Answer: A
Solution :
With temperature rise (same 25°C for both), steel scale and copper wire both expand. Hence length of copper wire w.r.t. steel scale or apparent length of copper wire after rise in temperature \[{{L}_{app}}=L{{'}_{cu}}-\,L{{'}_{steel}}=[{{L}_{0}}(1+{{\alpha }_{Cu}}\Delta \theta )-{{L}_{0}}(1+{{\alpha }_{s}}\Delta \theta )\] Þ \[{{L}_{app}}={{L}_{0}}({{\alpha }_{Cu}}-{{\alpha }_{s}})\Delta \theta \] \[=80(17\times {{10}^{-6}}-11\times {{10}^{-6}})\times 20\] = 80.0096 cm
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