An aluminium and steel rods having same lengths and cro... | null (Physics) | DivineJEE

JEE Mains 2026 21st January Shift 1

Physics

An aluminium and steel rods having same lengths and cross-sections are joined to make total length of

120\text{ cm}

30^\circ\text{C}

. The coefficient of linear expansion of aluminium and steel are

24 \times 10^{-6}/^\circ\text{C}

and

1.2 \times 10^{-5}/^\circ\text{C}

, respectively. The length of this composite rod when its temperature is raised to

100^\circ\text{C}

, is _____

\text{cm}

120.20

120.15

120.03

120.06

\ell_{\text{final}} = \ell_0(1 + \alpha_{\text{A}}\Delta\text{T}) + \ell_0(1 + \alpha_{\text{B}}\Delta\text{T})

= \ell_0[2 + (\alpha_{\text{A}} + \alpha_{\text{B}})\Delta\text{T}]

= 60[2 + (36 \times 10^{-6}) \times 70]

= 60[2 + 0.0025]

= 120.15 \text{ cm}

Select an option to instantly check whether it is correct or wrong.

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