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/, the lengths of the two rods are (a) lA = 200 cm, lB = 140 cm (b) lA = 180 cm, lB = 120 cm (c) lA = 160 cm, lB = 100 cm (d) lA = 120 cm, lB = 60 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 2023 (11 May, Shift 2)

Q37MHT CET 2023 · 11 MAY · SHIFT 2Medium

Thermometry & Thermal Expansion

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

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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 2023 (11 May, Shift 2)

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