Thermodynamics - 1 - Mechanical Engineering MCQ

A thermodynamic system is considered to be an isolated one if

The phenomenon of magnetic arc blow is observed almost exclusively with

Work transfer between the system and surround­ings

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

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

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

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

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

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

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