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Solution


Q.

An aluminium and steel rods having same lengths and cross-sections are joined to make total length of 120 cm at 30°C. The coefficient of linear expansion of aluminium and steel are 24×10-6/°C and 1.2×10-5/°C respectively. The length of this composite rod when its temperature is raised to 100°C, is ________ cm.   [2026]
1 120.20  
2 120.06  
3 120.03  
4 120.15  

Ans.

(4)

ℓfinal=ℓ0(1+αAΔT)+ℓ0(1+αBΔT)

         =ℓ0[2+(αA+αB)ΔT]

         =60[2+(36×10-6)×70]

         =60[2+0.0025]

          =120.15 cm