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JEE 2020 Physics: Heat Transfer Quiz (04.07.2019)

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Question 1

If the temperature of the sun were to increase from T to 2T and its radius from R to 2R, then the ratio of the radiant energy received on earth to what it was previously will be

Question 2

A long metallic bar is carrying heat from one of its ends to the other end under steady–state. The variation of temperature θ along the length x of the bar from its hot end is best described by which of the following figures?

Question 3

The temperature of two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity K and 2K and thickness x and 4x, respectively are T₂ and T₁ (T₂> T₁). The rate of Heat Transfer through the slab, in a steady state is

with f equal to

Question 4

One end of a thermally insulated rod is kept at a temperature T₁ and the other at T₂. The rod is composed of two sections of lengths l₁ and l₂ and thermal conductivities k₁ and k₂ respectively. The temperature at the interface of the two sections is

Question 5

A black coloured solid sphere of radius R and mass M is inside a cavity with vacuum inside. The walls of the cavity are maintained at temperature T₀. The initial temperature of the sphere is 3T₀. If the specific heat of the material of the sphere varies as

per unit mass with the temperature T of the sphere, where

is a constant, then the time taken for the sphere to cool down to temperature 2T₀ will be (

is Stefan Boltzmann constant)

Question 6

Two spheres of the same material have radii 1 m and 4 m and temperatures 4000 K and 2000 K respectively. The ratio of the energy radiated per second by the first sphere to that by the second is:

Question 7

Which of the following is more close to a black body?

Question 8

A, B and C are the three identical conductors but made from different materials. They are kept in contact as shown.
$Description: E:\KCET-1-Feb\KARNATAKA-PAPER-2012_files\image050.png$
Their thermal conductivities are K, 2K and $Description: E:\KCET-1-Feb\KARNATAKA-PAPER-2012_files\image051.png$ . The free end of A is at 100 ºC and the free end of C is at 0 ºC. During steady state, the temperature of the junction of A and B is nearly..... ºC.

Question 9

is the inversion temperature,

is the neutral temperature,

is the temperature of the cold junction then:

Question 10

Power emitted by a black body at temperature 50°C is P. Now temperature is doubled i.e. temperature of black body becomes 100 °C. Now power emitted is:

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