Consider the following properties:
Which of the above properties of a system is/are intensive?
(d) Intensive properties are independent of the mass in the system, for example, density, pressure, temperature. Extensive properties are related to mass, for example, volume, energy.
Pressure reaches a value of absolute zero
(d) Temperature and pressure are the measures of molecular moment of the system. The molecular moment of the system is zero, the absolute temperature and absolute pressure becomes zero.
Ice kept in a well insulated thermos flask is an example of which system?
(b) Heat and work cannot be transferred into the ice kept in a well insulated thermos flask, hence, it is an isolated system.
A thermodynamic system is considered to be an isolated one if
(c) An isolated system has no interaction with its surroundings.
The phenomenon of magnetic arc blow is observed almost exclusively with
Work transfer between the system and surroundings
(d) The change in a property of a system is independent of the path the system follows during the change of state. Therefore, properties are point functions. Work transfer is not a property of the system.
A hot metal piece kept in air cools from 80°C to 70°C in t1 seconds, from 70°C to 60°C in t2 seconds and from 60°C to 50°C in t3 seconds, then
A cyclic heat engine does 50 kJ of work per cycle. If the efficiency of the heat engine is 75%, the heat rejected per cycle is
W = 50 KJ
η = 0.75
Heat rejected per cycle is determned as
It is proposed to build a refrigeration plant for cold storage to be maintained at — 3°C. The ambient temperature is 27° C. If 5 x 106 kJ/h of energy is tobe continuously removed from the cold storage, the minimum power required to run the refrigerator will be
T2 = 270 K
T1 = 27 + 273
= 300 K
A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigeration machine with all other conditions unchanged, the coefficient of performance will be
Given that ηe = 0.3 . The COP of the refrigerater is
A heat engine is supplied with 250 kJ/s of heat at a constant fixed temperature of 227° C. The heat is rejected at 27° C. The cycle is reversible, if the amount of heat rejected is
The minimum heat rejected by reversible cycle is given by
Which one of the following pairs best expresses a relationship similar to that expressed in the pair “pressure-volume” for a thermodynamic system undergoing a process?
A heat pump working on a reversed Carnot cycle has a COP of 5. If it works as a refrigerator taking 1 kW of work input, the refrigeration effect will be
COP of the heat Pump is
The COP of the refrigerater is
One reversible heat engine operates between 1600 K and T2 K, and smother reversible engine operates between T2 K and 400 K. If both engines have the same heat input and output, then the temperature T2 must be equal to
The given condition means equal efficiency of both engines , therefore
A heat engine using lake water at 12° C as source and the surrounding atmosphere at 2°C as sink executes 1080 cycles per minute. If the amount of heat drawn per cycle is 57 J, then the output of the engine will be