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1.0.0
MCQ
2121. Efficiency of a Carnot engine is given as 80%. If the cycle direction he reversed, what will be the value of COP of reversed Carnut cycle?
125
0.5
0.25
0.8
2122. Workdone in free expansion process is-
Zero
Minimum
Maximum
Positive
There is no restraining/opposing force or pressure as expansion occurs against vacuum. So, dw = 0 (in case of free expansion).
2123. An isobaric process, has constant-
Density
Temperature
Pressure
Volume
2124. Change in entropy in a irreversible process-
Ds>d𝘘
ds< d𝘘/T
Ds= d𝘘/T
De ɑ d𝘘 /T
2125. Where does the lowest temperature occur in a vapour compression cycle?
condenser
compressor
evaporator
expansion valve
2126. If the value of n = 0 in the equation PV^n = C, then the process is called-
Constant volume process
Adiabatic process
Constant pressure process
Isothermal process
Constant Pressure Process (n= 0) Isothermal Process (n = 1) [BREB-2014] Adiabatic Process (n = y) Polytropic Process (y> n > 1) Constant Volume Process (n = ∞) PV°=C ⇒ P=C [V°=1]
2127. In vapour compresion refrigeration system, refrigerant occurs as liquid between-.
condeuser and expäision valve
compressor and evaporator
expansion valve and evaporator
compressor and condenser
2128. The human body feels comfortable who the heat stored in the body is.
positive
zero
negative
none
2129. Calorie is a measure of-
Specific heat
Quantity of heat
Thermal capacity
Entropy
2130. A path 1-2-3 is given. A system absorbs 100 kj as heat and does 60kj of work while along the path 1-4-3, it does 20kj of work. The heat absorbed during the cycle 1-4-3 is-
-140kj
-80kj
-40kj
+60kj
For 1-2-3 cycle. 𝘘1-2-3 = 100 kj W1-2-3 = 60 kj We know, Heat = Internal energy + Work 𝘘1-2-3 = 𝘘1-2-3 + W1-2-3 𝘘1-2-3 = 𝘘1-2-3 - W1-2-3 𝘘1-2-3 = (100-60) kj = 40 kj Again, For 1-4-3 cycle, W1-4-3 = 20kj 𝘘1-2-3 = 𝘘1-4-3 =40kj Again, we know, 𝘘1-4-3 = 𝘘1-4-3 + W1-4-3 = 40 kj+20 kj = 60 kj For 1-2-3 cycle. 𝘘1-2-3 = 100 kj W1-2-3 = 60 kj We know, Heat = Internal energy + Work 𝘘1-2-3 = 𝘘1-2-3 + W1-2-3 𝘘1-2-3 = 𝘘1-2-3 - W1-2-3 𝘘1-2-3 = (100-60) kj = 40 kj Again, For 1-4-3 cycle, W1-4-3 = 20kj 𝘘1-2-3 = 𝘘1-4-3 =40kj Again, we know, 𝘘1-4-3 = 𝘘1-4-3 + W1-4-3 = 40 kj+20 kj = 60 kj
2131. Pick up the correct statement about giving up of heat from one medium to other in ammonia absorption system-
strong solution is weak solution
weak solution to strong solution
atozng solution to ammonia vapour
ammonia vapour to weak solution
2132. A process in which the temperature of the working substance remains constant during its expansion or compression is called-
Isothermal process
Hyperbolic process
Adiabatic process
Polytrophic process
2133. The entropy in an irreversible cyclic process.
Remain constant
Decreases
Increase
First increase then decrease
2134. Which is true for adiabatic process?
∆W = 0
∆Q = 0
∆W=0
∆P=0
2135. An ideal gas obeys the law-
PT = nR ̅V
PV=n/R ̅T
PV= nR ̅T
PV= nR ̅/T
2136. The ratio of specific heat at constant pressure (Cp) and specific heat at constant volume (Cv) is-
Equal to one
Less than one
Greater than one
None
2137. In a refrigeration cycle, the flow of refrigerant is controlled by –
compressor
evaporator
expansion valve
condenser
2138. A mixture of gas expands from 0.03m to 0.06^3m at a constant pressure of 1 mpa and absorbs 84kj of heat during the process. The change in internal energy of the mixture is-
30 kj
54 kj
84 kj
114 kj
2139. For the same heat input and same compression ration.
Otto cycle and diesel cycle are equally efficient
Otto cycle is less efficient than diesel cycle
Efficiency depends mainly on working substance
None of the above
2140. In a throttling process-
In a throttling process-
Temperature remains constant
Enthalpy remains constant
Volume remains constant