Nursing Elites

1. Psychrometrics is a branch of thermodynamics that deals with the properties of:

• A. Ideal gases.
• B. Magnetic materials.
• C. Mixtures of moist air and water vapor.
• D. Nuclear reactions.

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.

2. An object with a mass of 45 kg has momentum equal to 180 kg⋅m/s. What is the object’s velocity?

• A. 4 m/s
• B. 8.1 km/s
• C. 17.4 km/h
• D. 135 m/s

Correct answer: A

Rationale: The momentum of an object is calculated by multiplying its mass and velocity. Mathematically, momentum = mass x velocity. Given that the mass is 45 kg and the momentum is 180 kg⋅m/s, we can rearrange the formula to solve for velocity: velocity = momentum / mass. Plugging in the values, velocity = 180 kg⋅m/s / 45 kg = 4 m/s. Therefore, the object's velocity is 4 m/s. Choices B, C, and D are incorrect because they do not align with the correct calculation based on the given mass and momentum values.

3. What is the electric field inside a hollow conductor with a net charge?

• A. Remains constant
• B. Decreases
• C. Zero
• D. Becomes unpredictable

Correct answer: C

Rationale: The correct answer is C: Zero. According to Gauss’s Law, the electric field inside a hollow conductor (a conductor with no charge inside but a net charge on its surface) is zero. The charges reside on the outer surface of the conductor, causing the electric field inside to cancel out. Choices A, B, and D are incorrect because the electric field inside a hollow conductor with a net charge is not constant, does not decrease, and does not become unpredictable; it is zero due to the distribution of charges on its surface.

4. The Reynolds number (Re) is a dimensionless quantity used to characterize:

• A. Fluid density
• B. Flow regime (laminar vs. turbulent)
• C. Surface tension effects
• D. Buoyancy force magnitude

Correct answer: B

Rationale: The Reynolds number is a dimensionless quantity used to characterize the flow regime, specifically whether it is laminar (smooth) or turbulent (chaotic). It depends on the velocity of the fluid, its characteristic length (such as pipe diameter), and its viscosity. A low Reynolds number indicates laminar flow, while a high Reynolds number suggests turbulence. Choices A, C, and D are incorrect because the Reynolds number is not related to fluid density, surface tension effects, or buoyancy force magnitude.

5. Which of the following statements is true about a refrigerator?

• A. It operates on a Carnot cycle and removes heat from a cold reservoir at a lower temperature.
• B. It violates the first law of thermodynamics by creating cold.
• C. It increases the total entropy of the universe.
• D. It operates isothermally at both the hot and cold reservoirs.

Correct answer: A

Rationale: A refrigerator operates on a Carnot cycle by transferring heat from a cold reservoir to a hot reservoir. Choice A is correct because a refrigerator removes heat from a cold reservoir at a lower temperature. Choice B is incorrect as a refrigerator does not violate the first law of thermodynamics but rather requires work input to transfer heat. Choice C is incorrect as a refrigerator does not increase the total entropy of the universe. Choice D is incorrect because a refrigerator does not operate isothermally at both the hot and cold reservoirs.

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