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Saturday, 31 October

JEE Main 2021 · PhysicsNumerical answerNumerical valueMediumMulti-step

JEE Main 27 August 2021, Shift 1, Physics Q30

Question 30 of 90 in this shift, Physics question 30 of 30, Section B.

A rod CD of thermal resistance 10.0 KW−1^{-1} is joined at the middle of an identical rod AB as shown in figure. The ends A, B and D are maintained at 200∘200^\circC, 100∘100^\circC and 125∘125^\circC respectively. The heat current in CD is P watt. The value of P is __________.

The figure, in words

A T-shaped arrangement: horizontal rod AB with A at the left end (200°C) and B at the right end (100°C); a vertical rod joined at the middle of AB at point C and going down to end D (125°C).

Official answer

2

NTA final key.

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

Same idea in other shifts

Asked 6× in all
  1. 7 Apr 2025, Shift 2 · Q47Two cylindrical rods A and B made of different materials, are joined in a straight line. The ratios of lengths, radii and thermal…MediumNumerical value
  2. 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
  3. 27 Jul 2022, Shift 1 · Q37If K1K_1 and K2K_2 are the thermal conductivities, L1L_1 and L2L_2 are the lengths and A1A_1 and A2A_2 are the cross sectional areas of…MediumSingle correctHas a figure
  4. 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
  5. 26 Feb 2021, Shift 1 · Q9The temperature θ\theta at the junction of two insulating sheets, having thermal resistances R1\mathrm{R_1} and R2\mathrm{R_2} as well as…EasyDiagram basedHas 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. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.