A small change t can be affected either in source temperature T1 or the sink temperature T2. Which (out of change in T1 and T2) will result in higher efficiency?
Increase in T1
Decrease in T2
Efficiency will be equally affected
Two identical carnot engines A and B operate between temperatures T1 and T2 with T1 greater than T2. subsequently the source temperature for engine A increases by and the sink temperature of engine B is decreased by . Then
Efficiency of engine A will become more
Engine B will become more efficient
Both the engines will have the same efficiency
The relative magnitude of T1, T2 and will determine which of the two engines is going to be more efficient
The coefficient of performance of a refrigeration working on a reversed carnot cycle is 4. the ratio of highest absolute temperature the lowest absolute temperature is
1.2
1.25
3.33
4
A heat pump working on a reversed carnot cycle has a COP of 5. if it works as a refrigerator taking 1Kw of work input, the refrigeration effect will be
1kW
2 kW
3 kW
4 kW
One reversible heat engine operates between 1600 K and T2K, and another reversible heat engine operates between T2K and 400K. if both the engines have the same heat input and output, the temperature T2 must be equal to
800K
1000K
1200K
1400K
A refrigeration machine working on reversed carnot cycle takes out 2kW per minute of heat from the system while working between the temperatures limits of 300K and 200K. then the co-efficient of performance and power consumed by the cycle will be respectively:
1 and 1 kW
1 and 2 kW
2 and 1 kW
2 and 2 kW
Which one of the following changes or sets of changes in the sources and sink temperature (T1 and T2 respectively) of a reversible engine will result in the maximum improvement in efficiency?
T1+
T2-
T1+ and (T2-)
(T1+T) and (T2+T)
Which one of the following is a correct statement?
A block slides down a rough plane and becomes cooler
Complete conversion of heat into work is possible
Thermodynamic temperature scale is independent of the nature of working substance
Negative temperatures can be attained on the absolute temperature scale
For a thermodynamic cycle to be irreversible, it is necessary that
=0
<0
>0
=0
An engine is supplied with 1120 kJ/s of heat and the source and sink are maintained at constant fixed temperatures of 560 K and 280 K respectively. If heat rejection is 840 kJ/s, indicate whether the given cycle is
Reversible
Irreversible
Impossible
Unpredictable; insufficient data
The relation ds=/T for entropy change during a process is valid for
All real processes
Only for reversible processes
Only for irreversible processes
Both for reversible and irreversible processes
When a system undergoes a process such that Q/T=0 and s>0, the process is
Irreversible adiabatic
Reversible adiabatic
Isothermal
Isobaric
A system undergoes a state change from 1 to 2. according to the second law of thermodynamic for the process to be feasible, the entropy change (s2-s1) of the system
Is positive or zero
Is negative or zero
Is zero
Can be positive, negative or zero
A system of 100 kg mass undergoes a process in which its specific entropy increases from 0.3 kJ/kg K to 0.4 kJ/kg K. at the same time, the entropy of the surroundings decreases from 80 kJ/kg K to 75 kJ/kg K. the process is:
Reversible and isothermal
Irreversible
Reversible
Impossible
The relation, T ds=du+p dv, is true for
Any system, any process
Any system, reversible process
Closed system, any process
Closed system and reversible processes only
Which one of the following statements applicable to a perfect gas will also be true for an irreversible process? (symbols have the usual meanings)
Tds=du+pdv
None
Which of the followings is a correct statement?
A reversible adiabatic process is an isentropic process
An irreversible adiabatic process is a constant entropy process
Entropy decreases during an irreversible adiabatic process
An isentropic process is an adiabatic process
The entropy of universe tends to
Become zero
Remain constant
Be maximum
Attain a certain finite minimum value
For any natural process, the entropy change would be
Zero
Positive
Negative
Unpredictable; insufficient data
The identity ds=R loge (p1/p2) determines the change in entropy of an ideal gas for a reversible process which is
Isobaric
Isochoric
Isothermal
Adiabatic