In fluid machinery, pumps are designed to primarily increase the fluid's:

Correct Answer: A

Rationale: Pumps in fluid machinery are designed to primarily increase the fluid's pressure. This increase in pressure allows the fluid to flow through the system efficiently and overcome resistance. While pumps can also impact the velocity of the fluid to some extent, their main function is to elevate the pressure to facilitate the movement of the fluid within the system. Choice B is incorrect because pumps do not focus solely on increasing velocity. Choice C is incorrect as while pumps can affect velocity, their primary purpose is to boost pressure. Choice D is incorrect as pumps aim to increase either the pressure, velocity, or both.

Correct Answer: A

Rationale: In an adiabatic process, choice A is correct because adiabatic processes involve no heat transfer between the system and its surroundings (Q = 0). This lack of heat transfer is a defining characteristic of adiabatic processes. Choices B, C, and D do not accurately describe an adiabatic process. Choice B refers to an isothermal process where temperature remains constant, not adiabatic. Choice C describes an isobaric process with constant pressure, not specific to adiabatic processes. Choice D mentions the conservation of energy but does not directly relate to the absence of heat transfer in adiabatic processes.

Correct Answer: C

Rationale: For a closed system undergoing a cyclic process and returning to its initial state, the net work done (Wnet) over the entire cycle can be positive, negative, or zero. This is because the work done is determined by the area enclosed by the cycle on a P-V diagram, and this area can be above, below, or intersecting the zero work axis, leading to positive, negative, or zero net work done. Choice A is incorrect because Wnet is not always positive; it depends on the specific path taken on the P-V diagram. Choice B is incorrect as Wnet is not always negative; it varies based on the enclosed area. Choice D is incorrect because Wnet is not necessarily equal to the total heat transferred into the system; it depends on the specifics of the cycle and is not a direct relationship.

Correct Answer: C

Rationale: During adiabatic compression, the gas's temperature increases. This is because no heat is exchanged with the surroundings, and all the work done on the gas results in an increase in internal energy. Choice A is incorrect because the temperature does not remain constant during adiabatic compression. Choice B is incorrect as the temperature does not decrease. Choice D is incorrect as the behavior of the gas's temperature during adiabatic compression is predictable based on the principles of thermodynamics.

Correct Answer: C

Rationale: Psychrometrics is the study of the physical and thermodynamic properties of gas-vapor mixtures, especially mixtures of moist air and water vapor. This branch of thermodynamics focuses on the relationships between temperature, pressure, humidity, and other properties of these mixtures. Choice A, ideal gases, is incorrect because psychrometrics specifically deals with gas-vapor mixtures, not ideal gases. Choice B, magnetic materials, and Choice D, nuclear reactions, are unrelated to psychrometrics and thermodynamics, making them incorrect. Understanding psychrometrics is crucial in fields like heating, ventilation, air conditioning, and refrigeration (HVAC&R) to design systems that effectively control air quality, comfort, and temperature.