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Saturday, 31 October

JEE Main 2022 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 27 July 2022, Shift 1, Physics Q37

Question 37 of 90 in this shift, Physics question 7 of 30, Section A.

If 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 steel and copper rods respectively such that K2K1=9\frac{K_2}{K_1}=9 , A1A2=2\frac{A_1}{A_2}=2, L1L2=2\frac{L_1}{L_2}=2. Then, for the arrangement as shown in the figure, the value of temperature T of the steel - copper junction in the steady state will be :

The figure, in words

A steel rod and a copper rod joined end to end in a line; the steel end is at the left labelled 'Furnace 450°C', the copper end at the right labelled 'Ice box 0°C'; the junction is marked with temperature T; 'Insulating material' is labelled below the rods, which are surrounded by it.
  1. (1)18°C
  2. (2)14°C
  3. (3)45°COfficial answer
  4. (4)150°C

Official answer

Option 3

NTA final key.

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

Same idea in other shifts

Asked 6× in all
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  3. 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
  4. 27 Aug 2021, Shift 1 · Q30A 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…MediumNumerical valueHas 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.