The difference in length between two rods A and B is 60 cm at all temperatures. If αA = 18 × 10⁻⁶/ and αB = 27 × 10⁻⁶/, then the length of rod A and rod B at 0 is respectively (a) lA = 120 cm, lB = 60 cm. (b) lA = 180 cm, lB = 120 cm. (c) lA = 240 cm, lB = 180 cm. (d) lA = 270 cm, lB = 210 cm.

Answer: (b). Constant difference: lAαA=lBαB⇒ 18 lA=27 lB⇒ lA=1.5 lB lA-lB=0.5 lB=60⇒ lB=120 cm, lA=180 cm So the answer is (b).

The difference in length between two rods A and B is 60 cm at all… | MHT CET 2025 (26 Apr, Shift 1)

Q19MHT CET 2025 · 26 APR · SHIFT 1Medium

Thermometry & Thermal Expansion

The difference in length between two rods A and B is 60 cm at all temperatures. If $\alpha_{\text{A}} = 18 \times 10^{-6}/^\circ\text{C}$ and $\alpha_{\text{B}} = 27 \times 10^{-6}/^\circ\text{C}$ , then the length of $\text{rod A}$ and $\text{rod B}$ at $0^\circ\text{C}$ is respectively

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Answer: (b)

Constant difference: $l_A\alpha_A=l_B\alpha_B\Rightarrow 18\,l_A=27\,l_B\Rightarrow l_A=1.5\,l_B$
$l_A-l_B=0.5\,l_B=60\Rightarrow l_B=120$ cm, $l_A=180$ cm
So the answer is (b).

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Thermometry & Thermal Expansion question from MHT CET 2025 (26 Apr, Shift 1)

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