### Eamcet - Physics - Thermodynamics

The relation between the coefficient of real expansion (γr) and coefficient of apparent expansion (γa) of a liquid and the coefficient of linear expansion (αg) of the material of the container is

A.  γr = αg + γa

B.  γr = αg + 3γa

C.  γr = 3αg + γa

D.  γr = 3(αg + γa )

The difference between volume and pressure coefficients of an ideal gas is :

A.  1/273

B.  273

C.  2/273

D.  0

The tyre of a motor car contains air at 150C. If the temperature increases to 350C, the approximate percentage increase in pressure is (ignore to expansion of tyre)

A.  7

B.  9

C.  11

D.  13

Two identical bodies have temperatures 2770C  and  670C. If the surroundings temperature is 270C, the ratio of loss of heats of the two bodies during the same interval of time is (approximately)

A.  4 : 1

B.  8 : 1

C.  12 : 1

D.  16 : 1

The ratio of specific heats of a gas is γ.The change in internal energy of one mole of the gas, when the volume changes from V to 2V at constant pressure P is

A.  γ-1 / PV

B.  PV

C.  PV / γ-1

D.  PV / γ

A liquid of mass m and specific heat S is heated to a temperature T. Another liquid of mass mil and specific heat 2 S is heated to temperature 2 T. If these two liquids are mixed, the resultant temperature of the mixture :

A.  2/3 T

B.  8/5T

C.  3/4T

D.  3/2T

A compound slab is made with two different materials A and B with coefficient of thermal  conductivity  KA = 2KB  and thickness XA=(1 / 2) XB. If the face of the A surface is at 1000C and that of the B surface is at 250C the temperature of the common surface will be

A.  850C

B.  450C

C.  400C

D.  150C

A clock which keeps correct time at 200C, is subjected to 400C. If coefficient of linear expansion of the pendulum is 12x 10-6 /0C. How much will it gain or lose time

A.  10.3 s/day

B.  20.6 s/day

C.  5 s/day

D.  20 min/day

Two gases A and B having same pressure P, volume V and absolute temperature T are mixed. If the mixture has the volume and temperature as V and T respectively, then the pressure of the mixture is

A.  2P

B.  P

C.  P/2

D.  4P

The temperature of the system decreases in the process of

A.  free expansion

C.  isothermal expansion

D.  isothermal compression

Two cylinders A and B fitted with pistons, contain equal number of moles of an ideal mono atomic gas at 400 K. The piston of A is free to move while that of B is held fixed. Same amount of heat energy is given to the gas in each cylinder. If the rise in temperature of the gas in A is 42 K, the rise in temperature of thegas in B is (γ = 5/3)

A.  25.2 K

B.  35 K

C.  42 K

D.  70 K

A black body radiates energy at the rate of E watt/m2 at a high temperature T K. When the temperature is reduced to (T/2) K, the radiant energy is

A.  E/2

B.  2E

C.  E/4

D.  E/16

A quantity of heat Q is supplied to a mono atomic ideal gas which expands at constant pressure. The fraction of heat that goes into work done by the gas is :

A.  2/5

B.  3/5

C.  2/3

D.  1

Calculate enthalpy for formation of ethylene from the following dataI. C(graphite)  + O2(g) ----->  CO2(g)   ∆H = 393.5kjII. H2(g) + (1/2) O2(g) ---------->  H2O(l) ∆H = -286.2kjIII.C2H4(g) + 3O2(g) ----------> 2CO2(g) + 2H2O(l)   ∆H = -1410.8kj

A.  54.1kj

B.  44.8kj

C.  51.4kj

D.  48.4kj

A clock pendulum made of invar has a period of 0.5 s , at 200 C . If the clock is used in a climate where the temperature averages to 300 C how much time does the clock loose in each oscillation (for invar α = 9 x 10-70 C and g = constant

A.  2.25 X 10-6 sec

B.  2.25 X 10-7 sec

C.  5 X 10-7 sec

D.  1.125 X 10-6 sec

A piece of metal weighs 45gms in air and 25gms in a liquid  of density 1.5 X 103 kg-m-3 kept at 300 C . When the temperature of the liquid is raised to 400 C the metal piece weighs 27gms . The density of the liquid at 400 C is 1.25 X 103 kg-m-3 . The coefficient of linear expansion of metal is

A.  1.3 X 10-3  / oC

B.  5.2 X 10-3  / oC

C.  2.6 X 10-3  / oC

D.  0.26 X 10-3  / oC

The temperature of a thin uniform circular disc, of one metre diameter is increased by 100C. The percentage increase in moment of inertia of the disc about an axis passing through its centre and perpendicular to the circular face : (linear coefficient of expansion = 11 x l0-6/ 0C )

A.  0.0055

B.  0.011

C.  0.022

D.  0.044

A given mass of a gas is compressed isothermally until its pressure is doubled. It is then allowed to expand adiabatically until its original volume is restored and its pressure is then found to be 0.75 of its initial pressure.The ratio of the specific heats of the gas is approximately

A.  1.20

B.  1.41

C.  1.67

D.  1.83

Two solid spheres A and B made of the same material have radii rA and rB respectively. Both the spheres are cooled from the same temperature under the conditions valid for Newton's law of cooling. The ratio of the rate of change of temperature of A and B is :

A.  rA/rB

B.  rB/rA

C.  r2A/ r2B

D.  r2B/r2A

An ideal gas is subjected to a cyclic process involving four thermodynamic states; the amounts of heat (Q) and work (W) involved in each of these states are

A.  500 , 7.5%

B.  700, 10.5%

C.  1000, 21%

D.  1500 , 15%

Two cylinders 'A' and 'B' fitted with pistons contain equal number of moles of an ideal mono-atomic gas at 400 K. The piston of 'A' is free to move while that of 'B' is hold fixed. Same amount of heat energy is given to the gas in each cylinder. If the rise in temperature of the gas in 'A' is 42 K, the rise in temperature of the gas in 'B' is

A.  21 K

B.  35 K

C.  42 K

D.  70 K

An ideal gas at a pressure of 1 atm and temperature of 270C is compressed adiabatically until its pressure becomes 8 times the initial pressure, then final temperature is : (γ = 3/2)

A.  6270C

B.  3270C

C.  4270C

D.  41.250 C

In a chemical reaction, ΔH=150KJ and ΔS=100JK-1 at 300K. ΔG would be

A.  120KJ

B.  330KJ

C.  300KJ

D.  Zero

The temperature of 5 moles of a gas at constant volume is changed from 1000C to1200C The change In internal energy is 80J. The total heat capacity of the gas at constant volume will be in J/K is

A.  8

B.  4

C.  0.8

D.  0.4

One mole of a gas occupies 100 ml at 50 mm pressure.The volume of 2 mole of the gas at 100 mm pressure and same temperature is

A.  50 ml

B.  100 ml

C.  200 ml

D.  500 ml

The radiation emitted by a star A is 10,000 times that of the sun. If the surface temperatures of the sun and the star A are 6000 K and 2000 K respectively, the ratio of the radii of the star A and the sun is:

A.  300 : 1

B.  600 : 1

C.  900: 1

D.  1200 : 1

Two cylindrical conductors A and B of same metallic material have their diameters in the ratio 1 : 2 and lengths in the ratio 2 : 1. If the temperature difference between their ends is same, the ratio of heats conducted respectively by A and B per sec is:

A.  1 : 2

B.  1 : 4

C.  1 : 16

D.  1 : 8

A vessel is filled with an ideal gas at a pressure of 10 atmosphere and temperature 270C. Half of the mass of the gas is removed from the vessel and temperature of the remaining gas is increased to 870C.Then the pressure of the gas in the vessel will be

A.  5 atm

B.  6 atm

C.  7 atm

D.  8 atm

The liquids at temperature 600C and 300C respectively have masses in the ratio 3 : 4 and their specific heats in the ratio 4 : 5. If the two liquids are mixed, the resultant temperature is:

A.  700C

B.  350C

C.  400C

D.  41.250C

A liquid of mass ‘m’ and specific heat C is heated to a temperature 2T.Anither liquid of mass m/2 and specific heat 2C is heated to a a temperature T.If these two liquids are mixed,the resulting temperature of mixture is

A.  (2/3)T

B.  (8/5)T

C.  (3/5)T

D.  (3/2)T