NEET Physics Thermodynamics Cyclic Process,Heat Engine,Refrigerator MCQs

A heat engine operates between two reservoirs at temperatures $T_1$ and $T_2$ ($T_1 > T_2$). It absorbs $Q_1$ heat from the hot reservoir and rejects $Q_2$ heat to the cold reservoir. If the engine's efficiency is half the Carnot efficiency, which of the following relations is correct?

A refrigerator operates between two reservoirs at temperatures $T_C$ and $T_H$ ($T_H > T_C$). It extracts $Q_C$ heat from the cold reservoir and rejects $Q_H$ heat to the hot reservoir. If the coefficient of performance (COP) is half the ideal COP, what is the relationship between $Q_H$ and $Q_C$?

In a cyclic process depicted on a P-V diagram, the work done by the system is equal to:

A reversible heat engine operates between three thermal reservoirs at temperatures $T_1$, $T_2$, and $T_3$ ($T_1 > T_2 > T_3$). It absorbs $Q_1$ heat from the $T_1$ reservoir, rejects $Q_3$ heat to the $T_3$ reservoir, and exchanges $Q_2$ heat with the $T_2$ reservoir (either absorbing or rejecting). What is the efficiency of this engine?

A real refrigerator working between two thermal reservoirs has a COP of 4. If it is used as a heat pump between the same reservoirs, its COP will be:

A Carnot engine absorbs heat $Q_1$ from a reservoir at temperature $T_1$ and rejects heat $Q_2$ at $T_2$. If $T_1$ is increased while keeping $Q_1$ constant, what happens to $Q_2$ and the net work done ($W$) by the engine?

In a cyclic process, the change in internal energy of the system is:

The efficiency of a heat engine is always:

Which of the following is the working principle of a refrigerator?

In a Carnot cycle, what is the relationship between the temperatures of the hot ($T_H$) and cold ($T_C$) reservoirs and the efficiency ($\eta$)?