Work done is zero for the following process
For constant volume process
Since, dV = 0
W = 0
For free expansion
W = 0
Also for throttling process
W = 0
In free expansion process
Which one of the following thermodynamic process approximates the steaming of food in a pressure cooker?
Since volume of pressure cooker is constant hence it is an Isochoric process.
The cyclic integral of (δQ - δW) for a process is
For a process
Heat transferred to a closed stationary system at constant volume is equal to
For constant volume, close system work = 0
δQ = dU
Thermodynamic work is the product of
The maximum amount of mechanical energy that can be converted into heat in any process
Since mechanical energy is high grade energy and heat is low grade energy, 100% conversion of high grade energy into low grade energy is possible.
The expression for work done during a process is applicable for
A paddle wheel used for stirring a liquid contained in a tank supplied 5000 kJ of work and during the stirring operation the tank lost 1500 kJ of heat to the surroundings. If the tank and liquid are considered as a system the change in its internal energy will be
From the first law of thermodynamics
δQ = dU + δW
-1500 = dU - 5000
dU = 5000 - 1500
dU = 3500 kJ
The change in enthalpy of a closed system is equal to the heat transferred, if the reversible process takes place at constant
Which one of the following statement holds good for the equation
This equation holds good for any process reversible or irreversible.
Change in internal energy in a reversible process occurring in a closed system is equal to the heat transferred, if the process occurs at constant
for constant volume process dV= 0
300 kJ/s of heat is supplied at a constant fixed temperature of 290°C to a heat engine. The heat rejection takes place at 8.5°C. Then match the following
Results obtained Cycle
A. 215 kJ/s are rejected 1. reversible
B. 150 kJ/s are rejected 2. irreversible
C. 75kJ/s are rejected 3. impossible
A B C
(a) 1 2 3
(b) 2 1 3
(c) 3 2 1
Match List-1 with List-11 and select the correct answer using the codes given below.
List - I
A. Work done
B. Thermal equilibrium
C. Internal energy
D. No work and heat interaction
List - II
1. Point function
2. Path function
3. Isolated system
4. Equality of temperature
A B C D
(a) 2 4 1 3
(b) 2 3 4 2
(c) 3 1 2 4
(d) 4 2 3 1
A 2 kW electric resistance heater submerged in 5 kg water is turned on and kept on for 10 min. During the process 300 kJ of heat is lost from the water the temperature rise of water is
P = 2 kW; Mass - 5 kg
Heat lost = 300 kJ
Heat supplied - 2 x 600 - 1200 kJ
Net heat supplied
= 1200 - 300
= 900 kJ
900 = 5 x 4.18 (ΔT)
ΔT = 43.1°C
One kg of ice at 0°C is completely melted into water at 0°C at 1 bar pressure. The latent heat of fusion of water is 333 kJ/kg and densities of water and ice at 0°C are 999 kg/m3 and 916 kg/m3 respectively. What are the approximate values of work done and energy transferred as heat for the process respectively.
Heat transfer = mL
= 1 x 333 = 333 kJ
It is desired to bring about a certain change in the state of a system by performing work on the system under adiabatic conditions.
Which one of the following statements is true?
The efficiency of a heat engine increases as the temperature of the heat source is increased while keeping the temperature of the heat sink fixed.
Match the following:
A. Heat I. State function
B. Internal energy II. Path function
Heat is a path function
Internal energy is a state function
Work is a path function
Entropy is a state function.
2 kg of steam in a piston-cylinder device at 400 kPa and 175°C undergoes a mechanically reversible, isothermal compression to a final pressure such that the steam becomes just saturated. What is the work, W, required for the process?
T = 175°C;
P = 400 kPa
v = 0.503 m3/kg
u = 2606 kJ/kg
s = 7.055 kJ/kgK
Saturated vapour, v = 0.216 m3/kg
u = 2579 kJ/kg, s = 6.622 kJ/kgK