Second Law Of Termodynamics – MSQ - Physics MCQ

All reversible engines have same efficiency only if they operate between same temperature and is given by 
The correct answer is: All the reversible engines operating between same temperatures have same efficiency

In adiabatic process, dQ = 0
⇒ 
⇒ S remains constant.
The correct answers are: Isothermal process, Cyclic process, Isobaric process

All the 3 options (a, b & c) results in the loss of heat and thus, result in irreversibility.
The correct answers are: mechanical and fluid friction, unrestricted expansion, heat transfer with a finite temperature difference 

From second law of thermodynamics, (a) and (b) are true.
In adiabatic process, dQ = 0
⇒ dS = 0, hence (c) is also true.
The correct answers are: Entropy increases during an irreversible operation   , Net change in entropy in a reversible cycle is zero, Change in entropy during an adiabatic operation is zero

Here, the only false statement is efficiency is equal to 1
∴ 
The correct answers are: work done in one cycle is Q₁ – Q₂, entropy of the hotter reservoir decreases, entropy for the universe (consisting of the working substance and the two reservoirs) increases

All the four options given above are necessary for reversibility of a cycle

The correct answers are: The pressure and temperature of working substance must not differ, appreciably from those of the surroundings at any stage in the process, All the processes taking place in the cycle of operation, must be extremely slow, The working parts of the engine must be friction free, There should be no loss of energy during the cycle of operation

(a, b, c) are all different definitions associated with the entropy and are thus all correct
The correct answers are: The increase in entropy is obtained from a given quantity of heat at a low temperature, The change in entropy may be regarded as a measure of the rate of the availability of heat for transformation into work., The entropy represents the maximum amount of work obtainable per degree drop in temperature

In reversible processes, change in entropy is zero but in irreversible process, change in entropy is positive. So, for any process, the change of entropy of the universe will be positive or zero.
The correct answers are: positive, zero

n=1-(TL/Tn)

For(a), n=1-(400/500) =1/5=0.2

For(b), n=1-(600/800) =1/4=0.25

For(c), n=1-(800/1000) =1/5=0.2

The option B and C is the correct answer.

Efficiency of Carnot engine doesn’t depend on working substance and its efficiency is always less than unity.
The correct answers are: Efficiency of a Carnot engine solely depends on hot and cold temperature reservoirs, Carnot engine has the maximum possible efficiency