2020
JEE Mains
MCQ
JEE Main 2020 (Online) 5th September Morning Slot
A bullet of mass 5 g, travelling with a speed of
210 m/s, strikes a fixed wooden target. One half
of its kinetic energy is converted into heat in
the bullet while the other half is converted into
heat in the wood. The rise of temperature of
the bullet if the specific heat of its material is
0.030 cal/(g – oC) (1 cal = 4.2 × 107 ergs) close
to :
A.
87.5 oC
B.
83.3 oC
C.
38.4 oC
D.
119.2 oC
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 4th September Evening Slot
Match the thermodynamic processes taking place in a system with the correct conditions. In the
table : $\Delta $Q is the heat supplied, $\Delta $W is the work done and $\Delta $U is change in internal energy of the
system.
| Process | Condition |
|---|---|
| (I) Adiabatic | (1) $\Delta $W = 0 |
| (II) Isothermal | (2) $\Delta $Q = 0 |
| (III) Isochoric | (3) $\Delta $U $ \ne $ 0, $\Delta $W $ \ne $ 0, $\Delta $Q $ \ne $ 0 |
| (IV) Isobaric | (4) $\Delta $U = 0 |
A.
(I) - (1), (II) - (1), (III) - (2), (IV) - (3)
B.
(I) - (2), (II) - (4), (III) - (1), (IV) - (3)
C.
(I) - (1), (II) - (2), (III) - (4), (IV) - (4)
D.
(I) - (2), (II) - (1), (III) - (4), (IV) - (3)
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 4th September Morning Slot
The specific heat of water
= 4200 J kg-1K-1 and the latent heat of
ice = 3.4 $ \times $ 105 J kg–1. 100 grams of ice at
0oC is placed in 200 g of water at 25oC. The
amount of ice that will melt as the temperature
of water reaches 0oC is close to (in grams) :
= 4200 J kg-1K-1 and the latent heat of
ice = 3.4 $ \times $ 105 J kg–1. 100 grams of ice at
0oC is placed in 200 g of water at 25oC. The
amount of ice that will melt as the temperature
of water reaches 0oC is close to (in grams) :
A.
63.8
B.
61.7
C.
69.3
D.
64.6
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 4th September Morning Slot
Match the ${{{C_P}} \over {{C_V}}}$ ratio for ideal gases with different type of molecules :
| Molecule Type | CP/CV |
|---|---|
| (A) Monatomic | (I) 7/5 |
| (B) Diatomic rigid molecules | (II) 9/7 |
| (C) Diatomic non-rigid molecules | (III) 4/3 |
| (D) Triatomic rigid molecules | (IV) 5/3 |
A.
(A)-(III), (B)-(IV), (C)-(II), (D)-(I)
B.
(A)-(IV), (B)-(II), (C)-(I), (D)-(III)
C.
(A)-(IV), (B)-(I), (C)-(II), (D)-(III)
D.
(A)-(II), (B)-(III), (C)-(I), (D)-(IV)
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 3rd September Evening Slot
To raise the temperature of a certain mass of gas by 50oC at a constant pressure, 160 calories of
heat is required. When the same mass of gas is cooled by 100oC at constant volume, 240 calories
of heat is released. How many degrees of freedom does each molecule of this gas have (assume
gas to be ideal)?
A.
6
B.
7
C.
5
D.
3
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 3rd September Evening Slot
A calorimeter of water equivalent 20 g contains 180 g of water at 25oC. ‘m’ grams of steam at
100oC is mixed in it till the temperature of the mixure is 31oC. The value of ‘m’ is close to :
(Latent heat of water = 540 cal g–1, specific heat of water = 1 cal g–1 oC–1)
(Latent heat of water = 540 cal g–1, specific heat of water = 1 cal g–1 oC–1)
A.
2.6
B.
2
C.
4
D.
3.2
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 3rd September Morning Slot
A balloon filled with helium (32oC and 1.7 atm.)
bursts. Immediately afterwards the expansion
of helium can be considered as
A.
Irreversible adiabatic
B.
Reversible adiabatic
C.
Irreversible isothermal
D.
Reversible isothermal
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 3rd September Morning Slot
Consider a gas of triatomic molecules. The
molecules are assumed to be triangular and
made of massless rigid rods whose vertices
are occupied by atoms. The internal energy of
a mole of the gas at temperature T is :
A.
${3 \over 2}RT$
B.
${9 \over 2}RT$
C.
${5 \over 2}RT$
D.
3RT
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 2nd September Evening Slot
A heat engine is involved with exchange of heat
of 1915 J, – 40J, + 125 J and –Q J, during one
cycle achieving an efficiency of 50.0%. The
value of Q is
A.
980 J
B.
40 J
C.
400 J
D.
640 J
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 2nd September Evening Slot
When the temperature of a metal wire is
increased from 0oC to 10oC, its length
increases by 0.02%. The percentage change in
its mass density will be closest to :
A.
0.008
B.
0.06
C.
0.8
D.
2.3
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 2nd September Evening Slot
An ideal gas in a closed container is slowly
heated. As its temperature increases, which of
the following statements are true?
(A) the mean free path of the molecules decreases.
(B) the mean collision time between the molecules decreases.
(C) the mean free path remains unchanged.
(D) the mean collision time remains unchanged.
(A) the mean free path of the molecules decreases.
(B) the mean collision time between the molecules decreases.
(C) the mean free path remains unchanged.
(D) the mean collision time remains unchanged.
A.
(C) and (D)
B.
(A) and (D)
C.
(B) and (C)
D.
(A) and (B)
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 2nd September Morning Slot
A gas mixture consists of 3 moles of oxygen
and 5 moles of argon at temperature T.
Assuming the gases to be ideal and the oxygen
bond to be rigid, the total internal energy (in
units of RT) of the mixture is :
A.
11
B.
20
C.
15
D.
13
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 9th January Evening Slot
Two gases-argon (atomic radius 0.07 nm,
atomic weight 40) and xenon (atomic radius
0.1 nm, atomic weight 140) have the same
number density and are at the same
temperature. The raito of their respective mean
free times is closest to :
A.
2.3
B.
1.83
C.
4.67
D.
3.67
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 9th January Morning Slot
Consider two ideal diatomic gases A and B at
some temperature T. Molecules of the gas A are
rigid, and have a mass m. Molecules of the gas
B have an additional vibrational mode, and
have a mass ${m \over 4}$
. The ratio of the specific heats ($C_V^A$ and $C_V^B$ ) of gas A and B, respectively is :
A.
7 : 9
B.
5 : 7
C.
3 : 5
D.
5 : 9
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 9th January Morning Slot
Which of the following is an equivalent cyclic
process corresponding to the thermodynamic cyclic
given in the figure ? where, 1 $ \to $ 2 is adiabatic.
(Graphs are schematic and are not to scale)
(Graphs are schematic and are not to scale)
A.
B.
C.
D.
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 8th January Evening Slot
Consider a mixture of n moles of helium gas
and 2n moles of oxygen gas (molecules taken
to be rigid) as an ideal gas. Its CP/CV value
will be :
A.
23/15
B.
67/45
C.
40/27
D.
19/13
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 8th January Evening Slot
A carnot engine having an efficiency of ${1 \over {10}}$ is
being used as a refrigerator. If the work done
on the refrigerator is 10 J, the amount of
heat absorbed from the reservoir at lower
temperature is :
A.
90 J
B.
99 J
C.
1 J
D.
100 J
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 8th January Morning Slot
A thermodynamic cycle xyzx is shown on a V-T diagram.
The P-V diagram that best describes this cycle
is :
(Diagrams are schematic and not to scale)
The P-V diagram that best describes this cycle
is :(Diagrams are schematic and not to scale)
A.
B.
C.
D.
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 8th January Morning Slot
The plot that depicts the behavior of the mean
free time t (time between two successive
collisions) for the molecules of an ideal gas, as
a function of temperature (T), qualitatively, is:
(Graphs are schematic and not drawn to scale)
(Graphs are schematic and not drawn to scale)
A.
B.
C.
D.
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 7th January Evening Slot
Two ideal Carnot engines operate in cascade (all heat given up by one engine is used by the other
engine to produce work) between temperature, T1
and T2
. The temperature of the hot reservoir of
the first engine is T1
and the temperature of the cold reservoir of the second engine is T2
. T is
temperature of the sink of first engine which is also the source for the second which is also the
source for the second engine. How is T related to T1
and T2
. If both engines perform equal amount
of work?
A.
$T = {{2{T_1}{T_2}} \over {{T_1} + {T_2}}}$
B.
$T = \sqrt {{T_1}{T_2}} $
C.
$T = {{{T_1} + {T_2}} \over 2}$
D.
T = 0
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 7th January Evening Slot
Under an adiabatic process, the volume of an ideal gas gets doubled. Consequently the mean
collision time between the gas molecule changes from ${\tau _1}$
to ${\tau _2}$
. If ${{{C_p}} \over {{C_v}}} = \gamma $ for this gas then a good
estimate for ${{{\tau _2}} \over {{\tau _1}}}$
is given by :
A.
${\left( 2 \right)^{{{1 + \gamma } \over 2}}}$
B.
2
C.
${\left( {{1 \over 2}} \right)^{{{1 + \gamma } \over 2}}}$
D.
${\left( {{1 \over 2}} \right)^\gamma }$
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 7th January Morning Slot
Two moles of an ideal gas with ${{{C_P}} \over {{C_V}}} = {5 \over 3}$
are mixed with 3 moles of another ideal gas
with ${{{C_P}} \over {{C_V}}} = {4 \over 3}$. The value of ${{{C_P}} \over {{C_V}}}$ for the
mixture is :
A.
1.50
B.
1.45
C.
1.47
D.
1.42
2020
JEE Mains
MCQ
JEE Main 2020 (Online) 7th January Morning Slot
A litre of dry air at STP expands adiabatically to a volume of 3 litres. If $\gamma $ = 1.40, the work done by air is : (31.4 = 4.6555) [Take air to be an ideal gas]
A.
60.7 J
B.
100.8 J
C.
90.5 J
D.
48 J
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th April Evening Slot
A diatomic gas with rigid molecules does 10 J of work when expanded at constant pressure. What would be
the heat energy absorbed by the gas, in this process ?
A.
35 J
B.
30 J
C.
25 J
D.
40 J
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th April Evening Slot
One kg of water, at 20oC, heated in an electric kettle whose heating element has a mean (temperature
averaged) resistance of 20 $\Omega $. The rms voltage in the mains is 200 V. Ignoring heat loss from the kettle, time
taken for water to evaporate fully, is close to :
[Specific heat of water = 4200 J/(kg oC), Latent heat of water = 2260 kJ/kg]
A.
10 minutes
B.
22 minutes
C.
3 minutes
D.
16 minutes
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th April Evening Slot
A Carnot engine has an efficiency of ${1 \over 6}$. When the temperature of the sink is reduced by 62ºC, its efficiency
is doubled. The temperatures of the source and the sink are, respectively
A.
99oC, 37oC
B.
124oC, 62oC
C.
37oC, 99oC
D.
62oC, 124oC
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th April Morning Slot
At 40o C, a brass wire of 1 mm radius is hung from the ceiling. A small mass, M is hung from the free end of
the wire. When the wire is cooled down from 40oC to 20oC it regains its original length of 0.2 m. The value
of M is close to :
(Coefficient of linear expansion and Young’s modulus of brass are 10–5
/oC and 1011 N/m
2
, respectively; g=
10 ms–2
)
A.
1.5 kg
B.
0.5 kg
C.
9 kg
D.
0.9 kg
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th April Morning Slot
Two moles of helium gas is mixed with three moles of hydrogen molecules (taken to be rigid). What is the
molar specific heat of mixture at constant volume ? (R = 8.3 J/mol K)
A.
21.6 J/mol K
B.
17.4 J/mol K
C.
15.7 J/mol K
D.
19.7 J/mol K
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th April Morning Slot
When M1 gram of ice at –10oC (specific heat = 0.5 cal g–1
oC–1
) is added to M2 gram of water at 50C, finally
no ice is left and the water is at 0°C. The value of latent heat of ice, in cal g–1
is :
A.
${{50{M_2}} \over {{M_1}}} - 5$
B.
${{50{M_2}} \over {{M_1}}}$
C.
${{5{M_2}} \over {{M_1}}} - 5$
D.
${{5{M_1}} \over {{M_2}}} - 50$
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th April Morning Slot
A sample of an ideal gas is taken through the cyclic process abca as shown in the figure. The change in the
internal energy of the gas along the path ca is –180 J. The gas absorbs 250 J of heat along the path ab and 60
J along the path bc. The work done by the gas along the path abc is:
A.
120 J
B.
130 J
C.
100 J
D.
140 J
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 10th April Evening Slot
One mole of ideal gas passes through a process where pressure and volume obey the relation
$P = {P_0}\left[ {1 - {1 \over 2}{{\left( {{{{V_0}} \over V}} \right)}^2}} \right]$.
Here P0 and V0 are constants. Calculate the change in the temperature of the gas if its
volume changes form V0 to 2V0
A.
${3 \over 4}{{{P_0}{V_0}} \over R}$
B.
${1 \over 2}{{{P_0}{V_0}} \over R}$
C.
${5 \over 4}{{{P_0}{V_0}} \over R}$
D.
${1 \over 4}{{{P_0}{V_0}} \over R}$
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 10th April Evening Slot
When heat Q is supplied to a diatomic gas of rigid molecules, at constant volume its temperature increases by
$\Delta $T. the heat required to produce the same change in temperature, at a constant pressure is :
A.
${7 \over 5}Q$
B.
${3 \over 2}Q$
C.
${2 \over 3}Q$
D.
${5 \over 3}Q$
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 10th April Morning Slot
A cylinder with fixed capacity of 67.2 lit
contains helium gas at STP. The amount of heat
needed to raise the temperature of the gas by
20°C is : [Given that R = 8.31 J mol–1 K–1]
A.
374 J
B.
700 J
C.
748 J
D.
350 J
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 10th April Morning Slot
n moles of an ideal gas with constant volume
heat capcity CV undergo an isobaric expansion
by certain volume. The ratio of the work done
in the process, to the heat supplied is :
A.
${{nR} \over {{C_V} - nR}}$
B.
${{4nR} \over {{C_V} - nR}}$
C.
${{4nR} \over {{C_V} + nR}}$
D.
${{nR} \over {{C_V} + nR}}$
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 10th April Morning Slot
A 25 × 10–3 m3 volume cylinder is filled with
1 mol of O2 gas at room temperature (300K).
The molecular diameter of O2, and its root
mean square speed, are found to be 0.3 nm, and
200 m/s, respectively. What is the average
collision rate (per second) for an O2 molecule ?
A.
~1013
B.
~1012
C.
~1011
D.
~1010
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 9th April Evening Slot
The specific heats, CP and CV of a gas of
diatomic molecules, A, are given (in units of
J mol–1 K–1) by 29 and 22, respectively.
Another gas of diatomic molecules, B, has the
corresponding values 30 and 21. If they are
treated as ideal gases, then :-
A.
A is rigid but B has a vibrational mode
B.
A has a vibrational mode but B has none
C.
A has one vibrational mode and B has two
D.
Both A and B have a vibrational mode each
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 9th April Evening Slot
A massless spring (k = 800 N/m), attached with
a mass (500 g) is completely immersed in 1 kg
of water. The spring is stretched by 2 cm and
released so that it starts vibrating. What would
be the order of magnitude of the change in the
temperature of water when the vibrations stop
completely ? (Assume that the water container
and spring receive negligible heat and specific
heat of mass = 400 J/kg K, specific heat of
water = 4184 J/kg K)
A.
10–3 K
B.
10–1 K
C.
10–5K
D.
10–4 K
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 9th April Evening Slot
Two materials having coefficients of thermal
conductivity '3K' and 'K' and thickness 'd' and
'3d', respectively, are joined to form a slab as
shown in the figure. The temperatures of the
outer surfaces are '$\theta $2' and '$\theta $1' respectively,
($\theta $2 > $\theta $1). The temperature at the interface is :-
A.
${{{\theta _1}} \over {10}} + {{9{\theta _2}} \over {10}}$
B.
${{{\theta _2} + {\theta _1}} \over 2}$
C.
${{{\theta _1}} \over {6}} + {{5{\theta _2}} \over {6}}$
D.
${{{\theta _1}} \over {3}} + {{2{\theta _2}} \over {3}}$
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 9th April Morning Slot
An HCl molecule has rotational, translational
and vibrational motions. If the rms velocity of
HCl molecules in its gaseous phase is $\overline v $ , m is
its mass and kB is Boltzmann constant, then its
temperature will be :
A.
${{m{{\overline v }^2}} \over {5{k_B}}}$
B.
${{m{{\overline v }^2}} \over {6{k_B}}}$
C.
${{m{{\overline v }^2}} \over {7{k_B}}}$
D.
${{m{{\overline v }^2}} \over {3{k_B}}}$
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 9th April Morning Slot
Following figure shows two processes A and
B for a gas. If $\Delta $QA and $\Delta $QB are the amount of
heat absorbed by the system in two cases, and
$\Delta $UA and $\Delta $UB are changes in internal energies,
respectively, then :
A.
$\Delta $QA > $\Delta $QB ; $\Delta $UA > $\Delta $UB
B.
$\Delta $QA < $\Delta $QB ; $\Delta $UA < $\Delta $UB
C.
$\Delta $QA > $\Delta $QB ; $\Delta $UA = $\Delta $UB
D.
$\Delta $QA = $\Delta $QB ; $\Delta $UA = $\Delta $UB
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 9th April Morning Slot
For a given gas at 1 atm pressure, rms speed
of the molecule is 200 m/s at 127°C. At 2 atm
pressure and at 227°C, the rms speed of the
molecules will be :
A.
100 m/s
B.
100 $\sqrt 5 $ m/s
C.
80 $\sqrt 5 $ m/s
D.
80 m/s
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 8th April Evening Slot
The temperature, at which the root mean square
velocity of hydrogen molecules equals their
escape velocity from the earth, is closest to :
[Boltzmann Constant kB = 1.38 × 10–23 J/K Avogadro Number NA = 6.02 × 1026 /kg Radius of Earth : 6.4 × 106 m Gravitational acceleration on Earth = 10ms–2]
[Boltzmann Constant kB = 1.38 × 10–23 J/K Avogadro Number NA = 6.02 × 1026 /kg Radius of Earth : 6.4 × 106 m Gravitational acceleration on Earth = 10ms–2]
A.
3 × 105 K
B.
104 K
C.
650 K
D.
800 K
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 8th April Evening Slot
The given diagram shows four processes i.e.,
isochoric, isobaric, isothermal and adiabatic.
The correct assignment of the processes, in the
same order is given by :-
A.
d a b c
B.
a d b c
C.
d a c b
D.
a d c b
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 8th April Morning Slot
Two identical beakers A and B contain equal
volumes of two different liquids at 60°C each
and left to cool down. Liquid in A has density
of 8 × 102 kg/m3 and specific heat of
2000 J kg–1 K–1 while liquid in B has density
of 103 kg m–3 and specific heat of
4000 J kg–1 K–1. Which of the following best
describes their temperature versus time graph
schematically? (assume the emissivity of both
the beakers to be the same)
A.
B.
C.
D.
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 8th April Morning Slot
A thermally insulated vessel contains 150g of
water at 0°C. Then the air from the vessel is
pumped out adiabatically. A fraction of water
turns into ice and the rest evaporates at 0°C
itself. The mass of evaporated water will be
closest to :
(Latent heat of vaporization of water
= 2.10 × 106 J kg–1 and Latent heat of Fusion
of water = 3.36 × 105 J kg–1)
A.
35 g
B.
130 g
C.
20 g
D.
150 g
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th January Evening Slot
An ideal gas is enclosed in a cylinder at pressure of 2 atm and temperature 300 K. The mean time between two successive collisions is 6 $ \times $ 10–8 s. If the pressure is doubled and temperature is increased to 500 K, the mean time between two successive collisions will be close to
A.
0.5 $ \times $ 10$-$8 s
B.
4 $ \times $ 10$-$8 s
C.
3 $ \times $ 10$-$6 s
D.
2 $ \times $ 10$-$7 s
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th January Evening Slot
A vertical closed cylinder is separated into two parts by a frictionless piston of mass m and of negligible thickness. The piston is free to move along the length of the cylinder. The length of the cylinder above the piston is $\ell $1, and that below the piston is $\ell $2, such that $\ell $1 > $\ell $2. Each part of the cylinder contains n moles of an ideal gas at equal temperature T. If the piston is stationary, its mass, m, will be given by :
(R is universal gas constant and g is the acceleration due to gravity)
(R is universal gas constant and g is the acceleration due to gravity)
A.
${{nRT} \over g}\left[ {{{{\ell _1} - {\ell _2}} \over {{\ell _1}{\ell _2}}}} \right]$
B.
${{RT} \over g}\left[ {{{2{\ell _1} + {\ell _2}} \over {{\ell _1}{\ell _2}}}} \right]$
C.
${{nRT} \over g}\left[ {{1 \over {{\ell _2}}} + {1 \over {{\ell _1}}}} \right]$
D.
${{RT} \over {ng}}\left[ {{{{\ell _1} - 3{\ell _2}} \over {{\ell _1}{\ell _2}}}} \right]$
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th January Morning Slot
For the given cyclic process CAB as shown for a gas, the work done is :
A.
1 J
B.
10 J
C.
5 J
D.
30 J
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th January Morning Slot
An ideal gas occupies a volume of 2m3 at a pressure of 3 $ \times $ 106 Pa. The energy of the gas is :
A.
6 $ \times $ 104 J
B.
9$ \times $ 106 J
C.
3 $ \times $ 102 J
D.
108 J
2019
JEE Mains
MCQ
JEE Main 2019 (Online) 12th January Morning Slot
A cylinder of radius R is surrounded by a cylindrical shell of inner radius R and outer radius 2R. The thermal conductivity of the material of the inner cylinder is K1 and the of the outer cylinder is K2. Assuming no loss of heat, the effective thermal conductivity of the system for heat flowing along the length of the cylinder is :
A.
K1 + K2
B.
${{{K_1} + 3{K_2}} \over 4}$
C.
${{{K_1} + {K_2}} \over 2}$
D.
${{2{K_1} + 3{K_2}} \over 5}$
