MCQ
2241. A perpetual motion machine is-
A thermodynamic machine
A non-thermodynamic machine
A hypothetical machine
A hypothetical machine whose operation would violate the laws of thermodynamics
2242. যখন অ্যাবজরতিটি (∝) = 0, রিফ্লেকটিভিটি (p) = 1 এবং ট্রান্সমিটিভিটি (γ) = 0, তখন বস্তুটিকে কী বলা হবে?
কালো বস্তু
ধূসর বস্তু
ওপেক বস্তু
সাদা বস্তু
2243. Air-conditioning means.....
cooling
heating
dehumidifying
all of these
2244. Moisture in freon refrigeration system causes-
ineffective refrigeration
high power consumption
freezing automatic regulating valve
corrosion of whole system
2245. Superheating in a refrigeration cycle-
increases COP
decreases COP
COP remains unaltered
other factors decide COP
2246. For proper refrigeration in a cabinet, if the temperature and vapour pressure differenc between cabinet and atmosphere is high then-
bigger cabinet should be used
smaller cabinet should be used
perfectly tight vapour seal should be used
refrigerant with lower evaporation tempera should be used
2247. Choose the correct statement:
A refrigerant should have low latent heat
If operating temperature of system is low, then refrigerant with low boiling point should be used
Precooling and subcooling of refrigerant are same
Superheat and sensible heat of refrigerant are same
2248. The advantage of dry compression is that-
it permits higher speeds to be used
it permits complete evaporation in the evaporator
it results in high volumetire and mechanical efficiency
all of the above
2249. In a certain room, dry bulb temperature is 35°C and wet bulb temperature is also 35°C, the relative humdity of the room is-
80%
90%
100%
None of the above
2250. The gas constant (R) is equal to the of…. Two specific heats.
From first law of thermodynanties
Dq = du+dw
Mcpdt = mcdt+pdv ....................(1)
From ideal gas equation
PV = MRT
Pdv = mrdt
Dv = mrdt/P (2)
Now, substitute equation (2) in equation (1)
Mcpdt = mcvdt+mpr/P..................(2)
Cp=Cv+R
Cp – Cv = R
Product
Sum
Difference
Ratio
2251. Under-cooling in a refrigeration cycle-.
increases COP
decreases COP
COP remains unaltered
other factors decide COP
2252. The power per tonne of refrigeration is-
3.5/COP
COP/3.5
COP/ 35
3.5COP
2253. The minimum dielectric stress in a cable is at-.
conductor surface
centre of conductor
lead sheath
none of the above
2254. One ton of the refrigeration is-
the standard unit used in refrigeration problems
the cooling effect produced by melting 1 ton of ice
the refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C.in 24 hours
the refrigeration effect to produce 1 ton of ice at NTP conditions
2255. When two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. This statement is called-
Zeroth law of thermodynamics
First law of thermodynamics
Second law of thermodynamics
Kelvin Planck's law
2256. The suction pipe diameter of refrigerating unit compressor in comparison to delivery side is-.
bigger
smaller
equal
smaller/bigger depending on capacity
2257. For obtaining high COP, the pressure range of compressor should be--
high
optimum
low
any value
2258. 1 Ton of refrigeration is equivalent to heat removal rate of-
600 BTU/hr
10,000 BTU/hr
8000 BTU/hr
12,000 BTU/hr
2259. The absolute zero temperature is taken as-
-273°C
237°C
273°C
-237°C
2260. The pressure at the outlet of a refrigerant compressor is called-
discharge pressure
critical pressure
hack pressure
suction pressure