A reversible engine converts one-sixth of the heat input into work. When the temperature of the sink is reduced by 62°*C*, the efficiency of the engine is doubled. The temperatures of the source and sink are -

(1) 80°*C*, 37°*C*

(2) 95°*C*, 28°*C*

(3) 90°*C*, 37°*C*

(4) 99°*C*, 37°*C*

Concept Questions :-

Heat engine and refrigerator

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An ideal gas expands in such a manner that its pressure and volume can be related by equation $P{V}^{5/3}=cons\mathrm{tan}t$. During this process, the gas is

(1) Heated

(2) Cooled

(3) Neither heated nor cooled

(4) First heated and then cooled

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*P-V* diagram of a diatomic gas is a straight line passing through origin. The molar heat capacity of the gas in the process will be -

(1) 4 *R*

(2) 2.5 *R *

(3) 3 *R*

(4) $\frac{4R}{3}$

Concept Questions :-

Molar Specific heat

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Following figure shows on adiabatic cylindrical container of volume *V*_{0} divided by an adiabatic smooth piston (area of cross-section = *A*) in two equal parts. An ideal gas $({C}_{P}/{C}_{V}=\gamma )$ is at pressure *P*_{1} and temperature *T*_{1} in left part and gas at pressure *P*_{2} and temperature *T*_{2} in right part. The piston is slowly displaced and released at a position where it can stay in equilibrium. The final pressure of the two parts will be (Suppose *x* = displacement of the piston)

(1) *P*_{2}

(2) *P*_{1}

(3) $\frac{{P}_{1}{\left(\frac{{V}_{0}}{2}\right)}^{\gamma}}{{\left(\frac{{V}_{0}}{2}+Ax\right)}^{\gamma}}$

(4) $\frac{{P}_{2}{\left(\frac{{V}_{0}}{2}\right)}^{\gamma}}{{\left(\frac{{V}_{0}}{2}+Ax\right)}^{\gamma}}$

Concept Questions :-

Types of processes

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Two cylinders *A* and *B* fitted with pistons contain equal amounts of an ideal diatomic gas at 300 *K*. The piston of *A* is free to move while that of *B* is held fixed. The same amount of heat is given to the gas in each cylinder. If the rise in temperature of the gas in *A* is 30 *K*, then the rise in temperature of the gas in *B* is** **

(1) 30 *K*

(2) 18 *K*

(3) 50 *K*

(4) 42 *K*

Concept Questions :-

Molar Specific heat

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A system goes from *A* to *B* via two processes I and II as shown in figure. If Δ*U*_{I} and Δ*U*_{II} are the changes in internal energies in the processes I and II respectively, then

(1) Δ*U*_{II} > Δ*U*_{I}

(2) Δ*U*_{II} < Δ*U*_{I}

(3) Δ*U*_{I} = Δ*U*_{II}

(4) Relation between Δ*U*_{I} and Δ*U*_{II} can not be determined

Concept Questions :-

Basic terms

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A thermodynamic system is taken through the cycle *PQRSP* process. The net work done by the system is -

(1) 20 *J*

(2) – 20* J*

(3) 400* J*

(4) – 374* J *

Concept Questions :-

Cyclic process

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An ideal gas is taken around *ABCA* as shown in the above *P-V* diagram. The work done during a cycle is

(1) 2*PV*

(2) *PV *

(3) 1/2*PV *

(4) Zero

Concept Questions :-

Cyclic process

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The *P-V* diagram shows seven curved paths (connected by vertical paths) that can be followed by a gas. Which two of them should be parts of a closed cycle if the net work done by the gas is to be at its maximum value

(1) *ac*

(2) *cg*

(3) *af*

(4) *cd*

Concept Questions :-

Work done by gas

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An ideal gas of mass *m* in a state *A* goes to another state *B* via three different processes as shown in figure. If *Q*_{1}, *Q*_{2} and *Q*_{3} denote the heat absorbed by the gas along the three paths, then -

(1) *Q*_{1} < *Q*_{2} < *Q*_{3}

(2) *Q*_{1} < *Q*_{2} = *Q*_{3}

(3) *Q*_{1} = *Q*_{2} > *Q*_{3}

(4) *Q*_{1} > *Q*_{2} > *Q*_{3}

Concept Questions :-

First law of thermodynamics

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