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← JEE Main 2026 · 4 Apr · Shift 2
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JEE Main 2026 · 4 Apr · Shift 2, Physics question 34

The temperature of a metal strip having coefficient of linear expansion α\alpha is increased from T1T_1 to T2T_2 resulting in increase of its length by ΔL1\Delta L_1. The temperature is further increased from T2T_2 to T3T_3 such that the increase in its length is ΔL2\Delta L_2.
Given T3+T1=2T2T_3+T_1=2T_2 and T2−T1=ΔTT_2-T_1=\Delta T, the value of ΔL2\Delta L_2 is ________.

Choose one option
Answer and worked solution

Official answer: D

Same temperature step. T3−T2=T2−T1=ΔTT_3-T_2=T_2-T_1=\Delta T, but the second step starts from the longer length L(1+αΔT)L(1+\alpha\Delta T).

So ΔL2=L(1+αΔT)αΔT=ΔL1(1+αΔT)\Delta L_2=L(1+\alpha\Delta T)\alpha\Delta T=\Delta L_1(1+\alpha\Delta T).

(D)