Recent questions and answers in Thermodynamics

Which one of the graphs below best illustrates the relationship between internal energy U and temperature T of the gas in K ?

answered Apr 22, 2014 by yamini.v

1 answer

$\;C_{p}\;$ and $\;C_{v}\;$ denote the molar specific heat capacities of a gas at constant pressure and constant volume respectively . Then

answered Apr 22, 2014 by yamini.v

1 answer

An ideal gas initially at a state $\;(P_{1},V_{1})\;$ is allowed to expand isothermally to a state $\;(P_{2},V_{2})\;$ . Then the gas is compressed adiabatically to its initial volume $\;V_{1}\;$ . Let the final pressure be $\;p_{3}\;$ and the workdone by the gas be W , Then

answered Apr 9, 2014 by yamini.v

1 answer

A sample of an ideal gas is taken through the process ABCA shown . It rejects 50 J of heat during part AB , does not absorb or reflect heat during BC and accepts 70 J of heat during CA . Forty joules of work is done on the gas during the part BC . The internal energies at B and C respectively will be $\;(u_{A} =1500\;J)$

answered Apr 9, 2014 by yamini.v

1 answer

Logarithms of readings of pressure and volume from ideal gas were plotted on a graph as shown . By measuring the gradient , it can be shown that the gas may be

answered Apr 9, 2014 by yamini.v

1 answer

An ideal gas is filled in a closed rigid and thermally insulated container . A coil of 100 oms resistor carrying a current of 1 A for 5 minutes supplies heat to the gas . The change in the internal energy of the gas is

answered Apr 9, 2014 by yamini.v

1 answer

An ideal gas is taken through the cycle $\;A \to B \to C \to A \;$ as shown in the figure . If the net heat supplied to the gas in the cycle is 5 J , the work done by the gas is the process $\;C \to A\;$ is

answered Apr 9, 2014 by yamini.v

1 answer

Starting from the same initial conditions , an ideal gas expands from volume $\;V_{1}\;$ to $\;V_{2}\;$ in three different ways . The work done by the gas is $\;W_{1}\;$ if the process is purely isothermal , $\;W_{2}\;$ if purely isobaric and $\;W_{3}\;$ if purely adiabatic . Then :

answered Apr 9, 2014 by yamini.v

1 answer

A thermodynamics ideal gas , initially at temperature $\;T_{1}\;$ ia enclosed in a cylinder fitted with a friction less piston . The gas is allowed to expand adiabatically to a temperature $\;T_{2}\;$ by releasing the piston suddenly . If $\;L_{1}\;$ and $\;L_{2}\;$ are the lengths of gas column before and after expansion respectively , then $\;\large\frac{T_{1}}{T_{2}}\;$ is given by

answered Apr 9, 2014 by yamini.v

1 answer

A thermodynamic process , the pressures and volumes corresponding to some points in the figure are $\;P_{A} = 3 \times 10^{4}\;pa \;,V_{A} = 2 \times 10^{-3} \;m^3\;$ . $\;P_{B}=8 \times 10^{4}\;pa\;V_{D} = 5 \times 10^{-3}\;m^3\;$ . In the process AB , 600 J of heat and in the process BC , 200 J of heat is added to the system . The change in internal energy in process AC would be

answered Apr 9, 2014 by yamini.v

1 answer

Volume $\;V_{S}\;$ Temperature graph of two moles of helium gas is show in figure . The ratio of heat absorbed and the work done by the gas in process 1 - 2 is

answered Apr 9, 2014 by yamini.v

1 answer

A copper disc at $\;0^{0}C\;$ has a diameter of 50 cm and a hole is cut in the center with a diameter 5 cm . The diameter of the hole at $\;100^{0}C\;$ will be $\;(\alpha = 0.00016/^{0}C)\;$

answered Apr 8, 2014 by yamini.v

1 answer

A composite bar of length $\;(l_{1} + l_{2})\;$ is made from two bars of length $\;l_{1}\;$ and $\;l_{2}\;$ . Their coefficients of linear expansion $\;\alpha_{1}\;$ and $\;\alpha_{2}\;$ respectively . The effective linear coefficient of composite bar

answered Apr 8, 2014 by yamini.v

1 answer

When a block of iron floats in mercury at $\;0^{0}C\;$ , a fraction $\;K_{1}\;$ of its volume is submerged. While at the temperature $\;60^{0}C\;$ , a fraction $\;K_{2}\;$ is seen submerged . If the coefficient of volume expansion of iron is $\;r_{Fe}\;$ and that of mercury is $\;r_{Hg}\;$ , then the ratio $\;\large\frac{K_{1}}{K_{2}}\;$ can be expanded as

answered Apr 8, 2014 by yamini.v

1 answer

The apparent expansion of a liquid when heated in a copper vessel is C and when heated in a silver vessel is S . If A is coefficient of linear expansion of silver is

answered Apr 8, 2014 by yamini.v

1 answer

$\;l_{1}\;$ and $\;l_{2}\;$ are the lengths of two rods at $\;0^{0}C\;$ and have coefficients of linear expansion $\;\alpha_{1}\;$ and $\;\alpha_{2}\;$ respectively . If the difference between the lengths X is the same at all temperatures then $\;l_{1}\;$ is

answered Apr 8, 2014 by yamini.v

1 answer

A wire of length 60 cm is bent into a circle with a gap of 1 cm at its ends . On heating by by $\;100^{0}C\;$ , If the length of the gap increases to 1.02 cm , $\;\alpha\;$ of the material of the wire is

answered Apr 8, 2014 by yamini.v

1 answer

The brass scale of a barometer is correct at $\;0^{0}C\;$ and it reads 755 mm at $\;25^{0}C\;$ , Its reading at $\;0^{0}C\;$ is $\;r_{mercury} = 0.00018/^{0}C\;,r_{brass} =0.00021/^{0}C$

answered Apr 8, 2014 by yamini.v

1 answer

If the temperature of metal sphere increases by $\;\bigtriangleup t\;$ , the fractional change in its moment of inertia is $\;(\alpha \;= Coefficient\; of\; linear \;expansion )$

answered Apr 8, 2014 by yamini.v

1 answer

The wavelength $\;\lambda_{m}\;$ of maximum intensity of emission of solar radiation is $\;\lambda_{m}=14\; \mu m\;$ . The surface temperatures of sun and moon are (given $b= 2.898 \times 10^{-3} \; metre/Kelvin$ ).

answered Apr 8, 2014 by yamini.v

1 answer

A metal ball having surface area of $\;2 \times 10^{-2}\;m^2\;$ and at 900 K is kept in an enclosure at 300 K . If the surface emissivity of metal is 0.4 , find the rate of which heat is lost by the ball

answered Apr 8, 2014 by yamini.v

1 answer

A steel rod of length 20 cm and cross sectional area 3 $cm^{2}$ is heated at one end to $\;300^{0}C\;$ and the other end is in ice . Assuming no loss of heat , the mass of ice that melts in 10 minutes if $\;K_{steel} = 0.16 \;C.G.S\;$ units .

answered Apr 8, 2014 by yamini.v

1 answer

The temperature of a solid falls from $\;77^{0}C\;$ to $\;73^{0}C\;$ in 3 minutes and $\;73^{0}C\;$ to $\;69^{0}C\;$ in 4 minutes . What is the room temperature ?

answered Apr 8, 2014 by yamini.v

1 answer

The temperature of a solid falls from $\;72^{0}C\;$ to $\;60^{0}C\;$ in 10 minutes . How much time will it take to cool from $\;60^{0}C\;$ to $\;52^{0}C\;$ if the temperature of surroundings is $\;36^{0}C\;$ c ?

answered Apr 8, 2014 by yamini.v

1 answer

A copper rod AB of length 100 cm is fixed with a steel rod BC of length 20 cm at B . If the ends A and C are maintained at temperature $\;100^{0}C\;$ and $\;0^{0}C\;$ , then the temperature of the function B is : [thermal conductivities of copper and steel are 0.9 and 0.18 CGS units respectively ]

answered Apr 8, 2014 by yamini.v

1 answer

A cylinder of radius r and thermal conductivity $\;K_{1}\;$ is surrounded by cylindrical shell of inner radius r and outer radius 2r and thermal conductivity $\;K_{2}\;$ . The effective thermal conductivity when ends of combined system $\;t_{1}\;$ and $\;t_{2}\;$ under steady state is

answered Mar 31, 2014 by yamini.v

1 answer

If the temperature of a body is raised by $\;5 \%\;$ . Find increase in radiated energy .

answered Mar 26, 2014 by yamini.v

1 answer

Find the temperature at which a black body radiates energy at the rate of $\;5.67\;W/cm^{2}\;$

answered Mar 26, 2014 by yamini.v

1 answer

Two spheres of same material and radii 4 m and 1 m at temperature 1000 K and 2000 K . Find the ratio of the energies radiated by them in one second .

answered Mar 26, 2014 by yamini.v

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The maximum emission wavelength at temperature 2000 K is $\;4 \mu m\;$ . The maximum wavelength corresponding to temperature 2400 K will be

answered Mar 26, 2014 by yamini.v

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Two identical rods A and B when joined in series conduct heat at a rate of 4 w at steady state . If they are connected in parallel , they conduct heat at rate of

answered Mar 25, 2014 by yamini.v

1 answer

The ends of a metal rod of length 60 cm are showing the steady temperature $\;70^{0}C\;$ and $\;30^{0}C\;$ is the steady state . The temperature of the rod at a distance of 15 cm from hot end is

answered Mar 25, 2014 by yamini.v

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Five rods of the same dimension are arranged as shown . AB are maintained at different temperatures . No Heat flows through the central rod ; then

answered Mar 25, 2014 by yamini.v

1 answer

Two metal rods have their thermal conductivities $\;K_{1}\;$ and $\;K_{2}\;$ in the ratio 3 : 2 so that their thermal resistance are the same . Then their lengths are is the ratio ( Area of C .S . are the same )

answered Mar 25, 2014 by yamini.v

1 answer