Properties Of Solids And Liquids Question 99

Question: A steel scale measures the length of a copper wire as 80.0cm, when both are at 20C (the calibration temperature for scale). What would be the scale read for the length of the wire when both are at 40C ? (Given asteel =11×106 per°C and acopper =17×106perC ) [CPMT 2004]

Options:

A) 80.0096cm

B) 80.0272cm

C) 1cm

D) 25.2cm

Show Answer

Answer:

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 Lapp=LcuLsteel=[L0(1+αCuΔθ)L0(1+αsΔθ)

therefore Lapp=L0(αCuαs)Δθ

=80(17×10611×106)×20 = 80.0096 cm



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