HESI Exams Quizlet Physics

Correct Answer: D

Rationale: The correct answer is D: Dry ice. Dry ice is solid carbon dioxide that sublimes directly into carbon dioxide gas without melting into a liquid state. This process can be observed in everyday situations, such as when dry ice "evaporates" in a cooler. Iron (A) and Silver (B) do not undergo sublimation but instead melt into liquid phases. Salt crystal (C) also melts into a liquid (brine solution) before evaporating.

Correct Answer: C

Rationale: The correct answer is C: "It operates isothermally at the hot and cold reservoir temperatures." This statement is NOT true about a Carnot cycle. A Carnot cycle consists of four reversible processes: isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression. During the isothermal process, the working substance absorbs heat at the hot reservoir temperature and releases heat at the cold reservoir temperature. This process does not occur at the exact temperature of the reservoirs; rather, it occurs at a range of temperatures within each reservoir. As such, the statement that it operates isothermally at the hot and cold reservoir temperatures is incorrect. In summary, the other choices are incorrect because: A is true as efficiency is determined by the reservoir temperatures, B is true as it is a reversible cycle, and D is true as the Carnot cycle is the most efficient heat engine between the same two temperatures.

Correct Answer: C

Rationale: When a charged particle moves through a vacuum at a constant speed, it generates both an electric and magnetic field. This phenomenon is described by Maxwell's equations in electromagnetism. The moving charge creates a changing electric field which, in turn, induces a magnetic field according to Faraday's law of electromagnetic induction. This interplay between electric and magnetic fields is fundamental to electromagnetism. Choice A is incorrect as the moving charge does not only generate an electric field. Choice B is incorrect because the moving charge does not only generate a magnetic field. Choice D is incorrect because a moving charged particle always generates both electric and magnetic fields due to the fundamental principles of electromagnetism.

Correct Answer: B

Rationale: Step 1: Work is defined as the product of force and displacement in the direction of the force. Step 2: In this scenario, the object is stationary, meaning there is no displacement. Step 3: Without displacement, work done is zero. Step 4: Therefore, the correct answer is B: Not performed. Summary: A: Incorrect because work requires displacement. C: Incorrect as partial work implies partial displacement, which is not the case here. D: Incorrect as it is conclusive that work is not performed due to the absence of displacement.

Correct Answer: B

Rationale: The correct answer is B: Permeability is preferred. High permeability in the core of an electromagnet enhances its magnetic field strength by allowing more magnetic flux to pass through, increasing the efficiency of the electromagnet. Resistivity (choice A) would hinder current flow, reducing magnetic field strength. Permittivity (choice C) is related to electric fields, not magnetic fields. Dielectric strength (choice D) is the ability of a material to withstand electric fields, not directly related to enhancing magnetic properties.