Learn

Friday, 16 October

JEE Main 2025 · PhysicsNumerical answerNumerical valueMediumCalculation

JEE Main 7 April 2025, Shift 2, Physics Q47

Question 47 of 75 in this shift, Physics question 22 of 25, Section B.

Two cylindrical rods A and B made of different materials, are joined in a straight line. The ratios of lengths, radii and thermal conductivites of these rods are: LALB=12\frac{L_A}{L_B}=\frac{1}{2}, rArB=2\frac{r_A}{r_B}=2 and KAKB=12\frac{K_A}{K_B}=\frac{1}{2}. The free ends of rods A and B are maintained at 400 K, 200 K, respectively. The temperature of rods interface is __________ K, when equilibrium is established.

Official answer

360

NTA final key.

Chapter
Thermal Properties of Matter
Topic
Heat Conduction
Idea tested
Junction Temperature

Same idea in other shifts

Asked 3× in all
  1. 13 Apr 2023, Shift 2 · Q53Two plates A and B have thermal conductivities 84 Wm−1K−184\ \mathrm{Wm^{-1}K^{-1}} and 126 Wm−1K−1126\ \mathrm{Wm^{-1}K^{-1}} respectively. They have same…EasyNumerical value
  2. 24 Jun 2022, Shift 1 · Q50Two metallic blocks M1M_1 and M2M_2 of same area of cross-section are connected to each other (as shown in figure). If the thermal…MediumSingle correctHas a figure

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.