HESI A2
HESI A2 Physics Quizlet
1. Entropy (S) is a thermodynamic property related to the system's disorder. According to the second law of thermodynamics, in a spontaneous process:
- A. The total entropy of the system and surroundings increases.
- B. The total entropy of the system and surroundings decreases.
- C. The total entropy of the system remains constant.
- D. The total entropy of the surroundings increases, while the system's entropy decreases.
Correct answer: A
Rationale: The second law of thermodynamics asserts that the entropy of an isolated system (or the combined system and surroundings) will always increase in a spontaneous process, reflecting an increase in disorder. Therefore, the correct answer is that the total entropy of the system and surroundings increases. Choice B is incorrect because entropy always tends to increase in a spontaneous process, as dictated by the second law of thermodynamics. Choice C is incorrect as entropy typically increases in natural processes. Choice D is incorrect because the second law of thermodynamics states that the total entropy of the system and surroundings always increases in a spontaneous process.
2. When light travels from air into a denser medium like glass, its speed:
- A. Increases
- B. Decreases
- C. Remains constant
- D. Becomes unpredictable
Correct answer: B
Rationale: When light travels from air into a denser medium like glass, its speed decreases. This is because the higher refractive index of the denser medium causes light to slow down as it propagates through the medium. Choice A is incorrect because the speed of light decreases in a denser medium. Choice C is incorrect because the speed of light changes when it enters a denser medium. Choice D is incorrect because the change in speed is predictable based on the refractive index of the medium.
3. In Einstein’s mass-energy equation, what is represented by c?
- A. Distance in centimeters
- B. The speed of light
- C. Degrees Celsius
- D. Centrifugal force
Correct answer: B
Rationale: In Einstein's mass-energy equation, E=mc^2, the symbol 'c' represents the speed of light in a vacuum, which is approximately equal to 3.00 x 10^8 meters per second. This equation demonstrates the equivalence of energy (E) and mass (m) and is a fundamental concept in the theory of relativity. Choice A is incorrect as 'c' does not represent distance in centimeters. Choice C is incorrect as 'c' does not represent degrees Celsius. Choice D is incorrect as 'c' does not represent centrifugal force.
4. In the mechanical power equation P = E / t, power is measured in ___________.
- A. ohms
- B. Joules
- C. volts
- D. watts
Correct answer: D
Rationale: In the mechanical power equation P = E / t, power is measured in watts. Watts are the standard unit of power in the International System of Units (SI), named after the Scottish engineer James Watt. Watts are defined as joules per second, reflecting the rate at which energy is transferred or converted. Ohms (choice A) are the unit of electrical resistance, Joules (choice B) are the unit of energy, and volts (choice C) are the unit of electric potential difference. Therefore, the correct answer is watts as it directly relates to power in the given equation.
5. When two long, parallel wires carry currents in the same direction, the wires will experience a force of:
- A. An unpredictable force depending on wire material
- B. Repulsion
- C. No force
- D. Attraction
Correct answer: D
Rationale: When two wires carry current in the same direction, they create magnetic fields that interact with each other. This interaction results in an attractive force between the wires due to the alignment of their magnetic fields. Choice A is incorrect because the force can be predicted based on the direction of the currents and the magnetic fields produced. Choice B is incorrect because when currents flow in the same direction, they do not repel each other. Choice C is incorrect because there is indeed a force present due to the interaction of magnetic fields, resulting in attraction between the wires.
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