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Molecular Physics | Thermodynamics
On a P-V diagram starting from an initial state P0 V0 plot an adiabatic expansion to 2V0 an isothermal expansion to 2V0 and an isobaric expansion to 2V0.
a) Use this graph to determine in which process the least work is done by the system
b) If, instead, the substance was compressed to V0/2, in which process would the least work done ?
c) Plot the processes of parts (a) and (b) on P-T diagram starting from P0 T0. Indicate expansions and compressions and be careful to show relative positions at the endpoints of each process.
a) Use this graph to determine in which process the least work is done by the system
b) If, instead, the substance was compressed to V0/2, in which process would the least work done ?
c) Plot the processes of parts (a) and (b) on P-T diagram starting from P0 T0. Indicate expansions and compressions and be careful to show relative positions at the endpoints of each process.
Molecular Physics | Thermodynamics
8. A rod 20 cm long, has both its ends maintained at 0*C at all times. At time t = 0 the
temperature distribution in the rod is
T (x,0) = { 50*C for 0<x<10cm
{0*C for 10cm<x<20cm
Obtain the temperature distribution u(x,t) in the rod if u(x,t) satisfies the diffusion
equation:
d^2 u(x,t) / dx^2 = 0.5 ( du(x,t)/dt )
temperature distribution in the rod is
T (x,0) = { 50*C for 0<x<10cm
{0*C for 10cm<x<20cm
Obtain the temperature distribution u(x,t) in the rod if u(x,t) satisfies the diffusion
equation:
d^2 u(x,t) / dx^2 = 0.5 ( du(x,t)/dt )
Molecular Physics | Thermodynamics
17 It is NOT possible to completely convert
heat into internal energy
mechanical energy into heat
internal energy into mechanical energy
internal energy into heat
18 The second law of thermodynamics
is a statement of the law of conservation of energy
say that heat cannot be completely converted into mechanical energy
is the basis for the definition of temperature
is the basis for the definition of internal energy
heat into internal energy
mechanical energy into heat
internal energy into mechanical energy
internal energy into heat
18 The second law of thermodynamics
is a statement of the law of conservation of energy
say that heat cannot be completely converted into mechanical energy
is the basis for the definition of temperature
is the basis for the definition of internal energy
Molecular Physics | Thermodynamics
15 The average kinetic energy of the molecules of an ideal gas in a close, rigid container is increased by a factor of 4. What happens to the pressure of the gas?
It remains constant
It increases by a factor 2
It increases by a factor of 4
It increases by a factor of 8
16 At what temperature will the root-mean-square speed of oxygen molecules have the value of 640 m/s? 1 kilomole of oxygen has a mass of 32kg.
252.5oC
332.3oC
272.2oC
373.2oC
It remains constant
It increases by a factor 2
It increases by a factor of 4
It increases by a factor of 8
16 At what temperature will the root-mean-square speed of oxygen molecules have the value of 640 m/s? 1 kilomole of oxygen has a mass of 32kg.
252.5oC
332.3oC
272.2oC
373.2oC
Molecular Physics | Thermodynamics
13 A 0.5kg piece of metal (c = 600/kgK) at 300 degree celcius is dumped into a large pool of water at 20 degrees celcius. Assuming the change in temperature of water to be negligible, calculate the overall change in entropy for the system
85.5J/K
67.4J/K
122.3J/K
202.3J/K
14 Calculate how much heat is needed to be supplied to a gas at a pressure of
1.25×105Pa
, such that the pressure increases by 25 per cent at constant volume, and the internal energy by 120J.
240J
120J
320J
480J
85.5J/K
67.4J/K
122.3J/K
202.3J/K
14 Calculate how much heat is needed to be supplied to a gas at a pressure of
1.25×105Pa
, such that the pressure increases by 25 per cent at constant volume, and the internal energy by 120J.
240J
120J
320J
480J
Molecular Physics | Thermodynamics
9 The first law of thermodynamics may be written in he form
ΔU=ΔQ+ΔW
, where the symbols have their usual meaning. Which of the following is correct for the case of an isothermal expansion of an ideal gas?
ΔW>0
ΔW=0
ΔU=0
ΔU>0
10 Which statement about internal energy is correct
The internal energy of a system can be be increased without transfer of energy by heating
The internal energy depends only on its temperature
When the internal energy of a system is increased, its temperature always rises
When two system have the same internal energy, they must be at the same temperature
ΔU=ΔQ+ΔW
, where the symbols have their usual meaning. Which of the following is correct for the case of an isothermal expansion of an ideal gas?
ΔW>0
ΔW=0
ΔU=0
ΔU>0
10 Which statement about internal energy is correct
The internal energy of a system can be be increased without transfer of energy by heating
The internal energy depends only on its temperature
When the internal energy of a system is increased, its temperature always rises
When two system have the same internal energy, they must be at the same temperature
Molecular Physics | Thermodynamics
7 Which of these determines whether or not heat flows in a system?
average speed of the consituent particles of the system
pressure difference between parts of the system
degree of hotness or coolness of the system
temperature difference between parts of the system
8 Which of the following is NOT true about conduction as a means of heat transfer?
transfer of heat occurs through sucessive collisions of the atoms or molecules
the average kinetic energy of the atoms or molecules is greater in the hot object than in the cold object
the transfer process requires a material medium for it to take place
there is net translational motion of the atoms or molecules from their mean equilibrium positions
average speed of the consituent particles of the system
pressure difference between parts of the system
degree of hotness or coolness of the system
temperature difference between parts of the system
8 Which of the following is NOT true about conduction as a means of heat transfer?
transfer of heat occurs through sucessive collisions of the atoms or molecules
the average kinetic energy of the atoms or molecules is greater in the hot object than in the cold object
the transfer process requires a material medium for it to take place
there is net translational motion of the atoms or molecules from their mean equilibrium positions
Molecular Physics | Thermodynamics
3 A scientist uses a scale Y for measuring temperature. In this scale, pure water melts at
10oY
and boils at
130oY
at standard atmospheric pressure. The scientist measures the temperature at which sodium melts to be
127oY
. Express this temperature in degrees Celsius
97.5oC
102.6oC
38.6oC
196.6oC
4 When the junctions of two dissimilar metals are maintained at different temperatures an electromotive force is is set up in the circuit of which these junctions are part. A pair of juntions of this kind and the effect are known respectively as
thermistor and Peltier effect
resistance thermometer and Joule effect
pyrometer and Joule effect
thermocouple and Seebeck effect
10oY
and boils at
130oY
at standard atmospheric pressure. The scientist measures the temperature at which sodium melts to be
127oY
. Express this temperature in degrees Celsius
97.5oC
102.6oC
38.6oC
196.6oC
4 When the junctions of two dissimilar metals are maintained at different temperatures an electromotive force is is set up in the circuit of which these junctions are part. A pair of juntions of this kind and the effect are known respectively as
thermistor and Peltier effect
resistance thermometer and Joule effect
pyrometer and Joule effect
thermocouple and Seebeck effect
Molecular Physics | Thermodynamics
18 An engine absorbs 2000J of heat from a hot reservoir and expels 750J to a cold reservoir during each operating cycle. How much work is done during the cycle?
1250J
750J
2000J
350J
19 An engine absorbs 2000J of heat from a hot reservoir and expels 750J to a cold reservoir during each operating cycle. What is the power output of the engine if each cycle lasts for 0.5 seconds?
750W
1750W
3000W
2500W
20 The first law of thermodynamics is a restatement of which of these laws?
conservation of charge
conservation of momentum
conservation of entropy
onservation of energy
1250J
750J
2000J
350J
19 An engine absorbs 2000J of heat from a hot reservoir and expels 750J to a cold reservoir during each operating cycle. What is the power output of the engine if each cycle lasts for 0.5 seconds?
750W
1750W
3000W
2500W
20 The first law of thermodynamics is a restatement of which of these laws?
conservation of charge
conservation of momentum
conservation of entropy
onservation of energy
Molecular Physics | Thermodynamics
15 In which of the following phenomena is surface tension important?
the floating of a boat in water
the floating of a steel wire in water
the floating of a ballon in air
the floating of a plastic sphere in water
16 Which of the following substances has the highest viscosity at room temperature?
Water
kerosine
palm oil
alcohol
17 An engine absorbs 2000J of heat from a hot reservoir and expels 750J to a cold reservoir during each operating cycle. What is the efficiency of the engine?
50%
62.5%
74.2%
85.6%
the floating of a boat in water
the floating of a steel wire in water
the floating of a ballon in air
the floating of a plastic sphere in water
16 Which of the following substances has the highest viscosity at room temperature?
Water
kerosine
palm oil
alcohol
17 An engine absorbs 2000J of heat from a hot reservoir and expels 750J to a cold reservoir during each operating cycle. What is the efficiency of the engine?
50%
62.5%
74.2%
85.6%
