HESI A2
HESI Exams Quizlet Physics
1. What is the main difference between a reversible and irreversible process in thermodynamics?
- A. Reversible processes involve heat transfer, while irreversible processes do not.
- B. Reversible processes occur instantaneously, while irreversible processes take time.
- C. Reversible processes can be run in both directions with the same outcome, while irreversible processes cannot.
- D. Reversible processes violate the first law of thermodynamics.
Correct answer: C
Rationale: A reversible process is an idealized process that can be reversed without leaving any change in either the system or the surroundings. In contrast, irreversible processes cannot be reversed and often involve entropy production or dissipation. Choice A is incorrect because both reversible and irreversible processes can involve heat transfer. Choice B is incorrect as the speed of a process does not determine its reversibility. Choice D is incorrect because reversible processes do not violate the first law of thermodynamics; they comply with it by maintaining a balance between energy inputs and outputs. Therefore, the correct answer is C, as it accurately captures the main difference between reversible and irreversible processes in thermodynamics.
2. An electromagnet is holding a 1,500-kg car at a height of 25 m above the ground. The magnet then experiences a power outage, and the car falls to the ground. Which of the following is false?
- A. The car had a potential energy of 367.5 kJ.
- B. 367.5 kJ of potential energy is converted to kinetic energy.
- C. The car retains potential energy of 367.5 kJ when it hits the ground.
- D. The car’s potential energy converts to kinetic energy and then to sound energy.
Correct answer: C
Rationale: When the car falls to the ground, its potential energy is converted to kinetic energy as it accelerates downwards. Upon impact with the ground, the car's kinetic energy is dissipated in various forms, such as sound energy, heat, and deformation energy. Therefore, the car does not retain its initial potential energy of 367.5 kJ when it hits the ground. Choice A is true because the potential energy of the car can be calculated as mgh = 1500 kg * 9.8 m/s^2 * 25 m = 367,500 J = 367.5 kJ. Choice B is true because as the car falls, its potential energy is converted to kinetic energy. Choice D is true as the kinetic energy is eventually dissipated into other forms upon impact.
3. An incandescent lamp consumes 60 Joules of energy per second. What is the power rating of this lamp?
- A. 1 Watt (W)
- B. 60 Watts (W)
- C. 1/60 Joules
- D. Impossible to determine without knowing the voltage
Correct answer: B
Rationale: Power is defined as energy consumed per unit time. If the lamp consumes 60 Joules of energy per second, the power rating is 60 Watts. Therefore, choice B is correct. Choice A ('1 Watt') is incorrect because the lamp consumes 60 Joules per second, not 1 Joule per second. Choice C ('1/60 Joules') is incorrect as it does not represent the power rating. Choice D ('Impossible to determine without knowing the voltage') is incorrect because power can be calculated using energy consumption per unit time without needing to know the voltage.
4. In terms of electrical conductivity, semiconductors fall between
- A. Conductors and insulators
- B. Conductors and superconductors
- C. Insulators and dielectrics
- D. Superconductors and insulators
Correct answer: A
Rationale: Semiconductors have electrical conductivities that lie between those of conductors (high conductivity) and insulators (low conductivity). This positioning makes choice A, 'Conductors and insulators,' the correct answer. Choice B, 'Conductors and superconductors,' is incorrect because superconductors have perfect conductivity, not intermediate like semiconductors. Choice C, 'Insulators and dielectrics,' is incorrect because dielectrics are a type of insulator, so it doesn't show the progression from high to low conductivity. Choice D, 'Superconductors and insulators,' is incorrect because superconductors have the highest conductivity, opposite to the role of semiconductors.
5. A wave moves through its medium at 20 m/s with a wavelength of 4 m. What is the frequency of the wave?
- A. 5 s−1
- B. 16 s−1
- C. 24 s−1
- D. 80 s−1
Correct answer: C
Rationale: The formula to calculate the frequency of a wave is given by:
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