Q.

A copper rod of 88 cm and an aluminium rod of unknown length have their increase in length independent of increase in temperature. The length of aluminium rod is(αCu=1.7×10-5K-1,αAl=2.2×10-5K-1)               [2019]

1 68 cm  
2 6.8 cm  
3 113.9 cm  
4 88 cm  

Ans.

(1)

As per question, ΔlCu=ΔlAl

or,   lCuαCuΔT=lAlαAlΔT

lAl=lCuαCuαAl=88×1.7×10-52.2×10-5=68 cm