Nokea
In a parallel circuit, the ___________ through each component is the same.
- A. current
- B. voltage
- C. resistance
- D. wattage
Correct Answer: A
Rationale: In a parallel circuit, the current through each component is the same. This is because the components in a parallel circuit are connected across the same voltage source, so they all experience the same voltage across their terminals. The total current entering the parallel circuit is then split up among the various components, but the current through each component remains the same as the total current. Choices B, C, and D are incorrect. In a parallel circuit, voltage across each component may vary, resistance may differ, and wattage is related to power, not the equality of current through each component.
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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.
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.
An object with a mass of 45 kg has momentum equal to 180 kgâ‹…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 kgâ‹…m/s, we can rearrange the formula to solve for velocity: velocity = momentum / mass. Plugging in the values, velocity = 180 kgâ‹…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.
At which point on a roller coaster does the car have the greatest potential energy?
- A. The start of the ride
- B. The highest peak
- C. The lowest trough
- D. The end of the ride
Correct Answer: B
Rationale: The correct answer is B, the highest peak. At the highest peak of the roller coaster, the car reaches its maximum height above the ground. This point represents the car's greatest potential energy because it has the highest potential to do work due to its elevated position. The potential energy is directly proportional to the height of an object, so the highest point on the roller coaster track corresponds to the car's greatest potential energy. Choices A, C, and D are incorrect because potential energy is highest at the peak due to its elevated position, not at the start of the ride, the lowest trough, or the end of the ride.
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.