HESI Exams Quizlet Physics

Correct Answer: C

Rationale: The correct answer is C: 49 N/cm. To calculate the spring constant, we use Hooke's Law: F = kx, where F is the force applied, k is the spring constant, and x is the displacement from equilibrium. Given F = mg (mass multiplied by gravity) and x = 10 cm = 0.1 m, we can solve for k: k = F/x = mg/x = 5 kg * 9.8 m/s^2 / 0.1 m = 49 N/cm. Choice A is incorrect as it is lower than the correct answer. Choices B and D are incorrect as they are higher than the correct answer.

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: B

Rationale: In an isobaric process (constant pressure), work done is given by W = PΔV. Since the pressure is constant, work done is directly proportional to the volume change. As volume increases, work is done by the system, making it positive. If volume decreases, work is done on the system, making it negative. Choice A is incorrect as work is done even if volume change is zero. Choice C is incorrect as work's sign depends on the direction of volume change. Choice D is incorrect as work done is indeed dependent on pressure and volume change in an isobaric process.

Correct Answer: C

Rationale: The correct answer is C because reversible processes can be run in both directions with the same outcome, while irreversible processes cannot. In a reversible process, the system and surroundings can be restored to their original states after the process is reversed, maintaining equilibrium. This is not possible in irreversible processes, where energy dissipation and entropy generation lead to permanent changes. Choices A, B, and D are incorrect because reversible processes can involve heat transfer, do take time, and do not violate the first law of thermodynamics.

Correct Answer: A

Rationale: Semiconductors fall between conductors and insulators in terms of electrical conductivity because they have conductivity levels higher than insulators but lower than conductors. Conductors have high conductivity due to abundant free electrons, while insulators have very low conductivity due to the lack of free electrons. Semiconductors can conduct electricity under certain conditions by manipulating the number of free electrons through doping or applying electric fields. Therefore, choice A is correct. Choices B, C, and D are incorrect because they do not accurately represent the conductivity levels of semiconductors in relation to other materials.